I have a few questions on the book listed, I hope the owners of the book or people who have read the book could answer them: (if I am going to buy it, I need the details, so be frank, no lies)

1. It's not available on the DnDBeyond App. How do I access it if I purchase it from DnDBeyond?

2. It claims to have details on running a campaign or something in Feywild. I need to know for certain, what exactly is in there? Like tons of NPCs? Lots of lores? Additional narrations and descriptions of Feywild? Insane numbers of unique monsters? Hoards of new magical items? (You don't have to give explicit details, but I want to know what is in the book)

3. In case if there are new monsters and NPCs, illustrations? I need something to work on for the narrative/description...

4. Are there any new mechanics or new sub-system in the book concerning encounters/downtime activities/etc.?

Thanks for answering those questions in advance. The grassroot children will thank you as well.

(One more question: I can't buy it from the app...can I access the content from the app by any means? XD The app really makes life easier)

You can access it by going to marketplace, view by category: sourcebooks, and it's in that list. Alternatively, just follow this link: https://www.dndbeyond.com/marketplace/sourcebooks/domains-of-delight-a-feywild-accessory

As for the rest of the question, I can't answer because I haven't purchased it. I'd speculate that since it's not in the app, then it won't be accessible by the app after purchase either. I'm happy to defer to someone that has purchased it and knows better, though.

2. It claims to have details on running a campaign or something in Feywild. I need to know for certain, what exactly is in there? Like tons of NPCs? Lots of lores? Additional narrations and descriptions of Feywild? Insane numbers of unique monsters? Hoards of new magical items? (You don't have to give explicit details, but I want to know what is in the book)

3. In case if there are new monsters and NPCs, illustrations? I need something to work on for the narrative/description..

.4. Are there any new mechanics or new sub-system in the book concerning encounters/downtime activities/etc.?

So in PDF form, and the layout is very close in typography and layout to all the other official D&D books, Domains of Delight is 34 pages.  However, note that what I'd call the actual Domains of Delight content is only the first 24 pages.  The last 10 pages are play aids specifically designed to support Wild Beyond the Witchlight: some cards, some dialogue snippets, and some forms.  All these things (except probably the dialogue snippets) could possibly be somehow used by a DM elsewhere besides WBtW but that would be more DM inspiration/whimsy than the book telling you how to do this.

As far as lots of monsters, armies of NPCs, hoards of magic items etc, none of that hyperbole.  I think the best reference point, if you're familiar with it is the designing Domains of Dread Chapter from Van Richtens Guide to Ravensloft.  If you pull that chapter out of VRGtR, that's basically the book.  Domains of Delight are parallel to Domains of Dread (I'd actually say almost too much so on the nose).

The book begins with a bit of an overview of the Feywild, and some "generic Feywild" info like Fey contracts, curses etc. and other sorts of lore adjacent info that would help a DM run a game venturing into the Feywild.  After that generic info, which also includes some tables to help determine some random Feywild circumstances on the fly like Fey weather, the rest of the book is a system guiding a DM through designing a Domain of Delight.  

You start by designing the Domain's ArchFey, which is more a guide to "flavor" than "crunch".  The system offered is more an exercise in determining personality, style, appearance, and the sorts of magics your Archfey will likely be most associated with.  There's no real guide to statting your creation other than references the DMG on building or modifying monsters.  While strongly intended to create the central personality of your Domain of Delight, this system could be useful in creating a pact Patron or other major power PCs may have to deal or otherwise contend with in play that's not taking place in the Feywild.

Next up designing the domain, which is basically a walk through of how to sort of micro-world building specific to Domains of Delight.  The Domains of Delight content concludes by presenting an example Archfey and their Domain.  

Is it worth a a bit more than a quarter of the price of a regular D&D Beyond book (with a third of the page count actually dedicated to supporting an adventure)?  If you're looking for crunch and stats, I think you might be disappointed.  If you're looking for food for thought on how to role play personalities and locations (like Domains of Dread and the Shadowfell, locations do have atmospheres which are very much like a personality, in some cases quite literally) it'd be more valuable to you.  I grabbed it off DMsGuild and don't regret it; but having said that, the Minsc and Boo book WotC put out through DMsGuild at the same time, while almost twice as expensive (and notoriously typo ridden, though I've largely been able to look past that) has much more stat block meat (158 pgs ~58 stat blocks based on a quick page through) while having a similar guide to world building and campaign design goal.  

Sounds ick.  There can be any number of ways to do creative lore and suggestions right, but that seems to be a true rarity in 5e.  I didn’t like it in VRGtR and I doubt I’d like it here.   Like like this need to be leavened with stats and mechanics, otherwise they are extremely lacking (IMO, obviously).

I’d actually say that Van Richten’s Guide to Ravenloft is worth it.  It has a few character options (I didn’t care for them but that’s me), a bunch of new monsters, mechanics for horror based traps and suggestions on creative thinking for creating horrifying monsters, and a wonderful adventure on horror based adventure design PLUS a sample adventure for levels 1 to 3 (which is a far superior introduction to Curse of Strahd than Death House).  The section on Domains mostly made me go “meh” and it didn’t help that all the Dread Lords of Ravenloft were simply the base level monsters from the MM but with a name.  By example, it’s easily spotted that Strahd is just a Vampire Mage with a unique set of lair actions. It’s one of the reasons people tinker and homebrew him (though the CR 27 version was a bit much).

I purchased it on D&D Beyond, so can give you some feedback about its utility in this site:

1. If you purchase it on the site, it will show up in your D&D Beyond App. 

2. It does not have any new monsters, or items. What it does have: Guidance on fleshing out the Fey Realms; some information on creating your own Archfey; some tables for rolling up quick Fey contracts and ways to break them; and a number of NPCs (without stat blocks) related to the Feywild. 

3. Not much in the way of new art, but the cards for the NPCs provide enough descriptor to at least give your players an idea of what they look like.

4. Not sure I would say there are full mechanics on the items you listed, but there are new mechanics about Fey contracts, something useful for any Fey campaign.

Overall, if you are looking for more things to integrate into the encounter builder or character sheets, this has nothing for you.

That said, even though it is just a wall of text, it is a pretty decent wall of text with some neat lore and things which would be helpful to any campaign involving the Fey, even if you do not go to the Feywild itself.

Especially given its low price point and the proceeds going to charity, well worth the purchase.

I grabbed it off DMsGuild and don't regret it; but having said that, the Minsc and Boo book WotC put out through DMsGuild at the same time, while almost twice as expensive (and notoriously typo ridden, though I've largely been able to look past that) has much more stat block meat (158 pgs ~58 stat blocks based on a quick page through) while having a similar guide to world building and campaign design goal.  

I would love for them to offer the Misnc and Boo Guide on D&D Beyond. Even though I already have the PDF, I'd probably buy it again.

Quote from Leo_Lionhart >>

Much appreciated. So much better than the other replies that yielded nothing. 

All good, nothing new provided doesn't matter much if I am truly seeking for more information regarding Feywild.

You did mention one of my other concerns though; Wild Beyond the Witchlight, if you compare the both books, which one of them give a holistic setup/sample to Feywild? (I don't have the Ravenloft book yet)

Since you mentioned Ravenloft BTW, I need to work on subjects in the Domains of Dread, do I need the entire Ravenloft book for all the details? The campaign will not involve the Domains of Dread mostly, just some of the inhabitants/monsters coming from there. I have Curse of Strahd, will that be sufficient to design inhabitants/monsters from there?

Thank you for explaining in so much details. That really helps me in making the final decision on which book to be purchased. 👍

If you're interested in a resource for running adventures in the Feywild, I'd say Domains of Delight will give you more bang for your buck, as well as more license to create the Feywild locales and personalities you want.  Wild Beyond the Witchlight is an adventure script with some Feywild context but no more guidance on how to go "bigger" or "beyond" what's in the script than any other D&D adventure, in fact I'd say there's less nudging for expansion than past adventures.  

Van Richten's Guide is also a fun book for DMs.  I do want to pause on you asking whether you "need" it or Domains of Delight.  I'm very much in the nothing is essential to running a 5e game other than the SRD camp.  Both VRGtR and DoD do provide some tools for DMs who want further guidance on using certain structures of the D&D cosmology (the Feywild and Shadowfell being "echo planes" of the prime, and then you have these constellations of domains affiliated with each echo though not as connected to the Prime) 5e offers as a sort of default.  Both books also sort of serve as genre cliff notes.  I think someone could do a great Feywild campaign if they were comfortable with the Monster Manual's contents and knew Alice and Wonderland, The Faerie Queen, maybe Much Ado About Nothing, and maybe something like James and the Giant Peach.  You could do Domains of Dread without VRGtR and instead watching 12 hours of Universal Monster movies and Creature Features.  There's a lot of ways to make a good game and/or get comfortable with themes/genre/tones a DMs not accustomed to running, DoD and VRGtR are certainly useful, especially for a DM not very familiar with the genres reflected in both, but I would never say they are essential.  They're style guides, and you're free to adhere to them, build off of them, or reject whole swaths of them.  

Strahd gives a DM a lot to run and play with, moreso that Witchlight in my opinion.  It's sort of funny.  Domains of Dread are supposed to be oppressive places, and (while I disagree with this framing) Domains of Delight are generally portrayed as more bountiful places; but Strahd offers a more sandboxy way to play than (again, in my opinion) Witchlight.  Strahd gives good advice on running horror in Strahd, particularly but not exclusively gothic horror.  VRGtR attempts to give pointers to a broader range of horror and how to world build in them.  Again, I don't think this content is essential, and there's plenty of freely available world building guidance in a number of venues, including here.

I actually have friends who lent me their copies to read before I finally settle in buying Strahd. Indeed, contents in Strahd are great inspirations for running a horror theme campaign. It also comes with the extra tools, which is probably why many recommended it to me.

I am fine with expanding on my own as long as the general direction is shown. I had run MoP and expanded/incorporated it into an entire campaign. Thank you for all the cross-references across so many titles, some of those considerations are key factors I couldn't have known without the book/books for comparison. I think I know exactly which book I should purchase next. 😉👍

Ah! It does appear on the app after purchase on site? I guess they don't allow that in-app purchase because the money will be taken by Apple/Google? Evil Apple and naughty Google are trying to take money from charities! XD

Okay, I got everything I need to make the final decision. Thank you for the additional information concerning the purchase and the book availability in the app. That helps a lot. 👍