Could a creature benefit from the same manual more than once? Seeing as certain races live past centuries, they could in theory reuse such a book again and again

NOTE: JUST FOUND OUT EVERY TURN ISN'T A HOUR I search and search some say 6 seconds some say 10 minutes Idk tbh I'm confused lmao

Well in theory. I'm a vampire and I have this book. A vampire is undead and undead doesn't die from age nor do they need food, water, or sleep. Since the vampire can live up to like billions. Since every turn is technically an hour and there are 876,000 hours in a century. Just start counting your friends/enemies/yourself turns if your undead and then in theory in 4,380,000 hours/turns you will have the stat of 30 (which is maximum no matter what) and your modifier will be a 10+. BUT this is not counting the studying time which is 48 hours within 6 days. The huge problem with this theory, if you do this and count the turns and stuff you are also aging your friends meaning your companions unless they are undead as well but if not they will be dead when you can use the book twice. The whole reason it says it will regain its magic in a century is that so people won't use it every 48 hours and they are too OP for any creature. What I will be doing is that when I use the book I will take -1 to whatever stat like wisdom or something so "IF" I have used it 5 times and my wisdom WAS 15 (+2 modifier) it would then be a 10 (+0 modifier) just to sorta even things out making sure I can't be too OP. If I am wrong with any of this information or whatever, please correct me.

Fun fact: stats over 20 is considered demi-god stats and stats that are 30 are considered God stats.

The website (www.tribality.com/2015/10/30/dd-5e-vampire-class-and-custom-backgrounds/)I use for the vampire class (I don't do everything it says I change some of it but) ONLY use this class with friends who don't mind having a vampire in there party and make sure to ask your DM if it's okay, you don't want to surprise your DM since vampires are OP in general whether from this website or not.

Quote from Smartbutterfly4 >>

NOTE: JUST FOUND OUT EVERY TURN ISN'T A HOUR I search and search some say 6 seconds some say 10 minutes Idk tbh I'm confused lmao

Well in theory. I'm a vampire and I have this book. A vampire is undead and undead doesn't die from age nor do they need food, water, or sleep. Since the vampire can live up to like billions. Since every turn is technically an hour and there are 876,000 hours in a century. Just start counting your friends/enemies/yourself turns if your undead and then in theory in 4,380,000 hours/turns you will have the stat of 30 (which is maximum no matter what) and your modifier will be a 10+. BUT this is not counting the studying time which is 48 hours within 6 days. The huge problem with this theory, if you do this and count the turns and stuff you are also aging your friends meaning your companions unless they are undead as well but if not they will be dead when you can use the book twice. The whole reason it says it will regain its magic in a century is that so people won't use it every 48 hours and they are too OP for any creature. What I will be doing is that when I use the book I will take -1 to whatever stat like wisdom or something so "IF" I have used it 5 times and my wisdom WAS 15 (+2 modifier) it would then be a 10 (+0 modifier) just to sorta even things out making sure I can't be too OP. If I am wrong with any of this information or whatever, please correct me.

Fun fact: stats over 20 is considered demi-god stats and stats that are 30 are considered God stats.

The website (www.tribality.com/2015/10/30/dd-5e-vampire-class-and-custom-backgrounds/)I use for the vampire class (I don't do everything it says I change some of it but) ONLY use this class with friends who don't mind having a vampire in there party and make sure to ask your DM if it's okay, you don't want to surprise your DM since vampires are OP in general whether from this website or not.

 Each round (not individual turn, full initiative order) is 6 seconds.

Why are you mentioning your homebrew race when there are official races which can easily live long enough to use this multiple times like Elves and Warforged?

And 6 seconds is one round, always has been since the beginning of 5e, don't know where you got 1 hour or 10 minutes from

I think He is thinking out of combat... time and actions out of combat can get weird. in combat time rounds have always been 6 seconds. however out of combat actions used to have take 10 and so on that can confused with in combat stuff. I guess that might confuse some people...

Quote from ShankMugen >>

And 6 seconds is one round, always has been since the beginning of 5e, don't know where you got 1 hour or 10 minutes from

 Back in 1st edition, a turn was 10 minutes. I don’t remember which edition ditched that measurement, but some old school DMs still remember that and might be the cause of Smartbutterfly4’s confusion.

Yep have to wait for that time and then can use it again. 

yes, just wait for 100 years. In fact, if a human uses some magic that keeps him in a state of suspended animation, like the Isolation spell (I don't know what the spell is called in the English version), using that spell in the right way, you can just skip the 100 years with your character, without spending your precious life time

Quote from Jaeger_Grayshield >>

Could a creature benefit from the same manual more than once? Seeing as certain races live past centuries, they could in theory reuse such a book again and again

 yes also get boon ofimortality so don't get magic aged or any aged

It doesn't specify any maximum to use, so that mean it can increase Con past 30?

Quote from PvZ_Prime >>

It doesn't specify any maximum to use, so that mean it can increase Con past 30?

 No, I believe the soft cap for stats in 5e is 20 and the hard cap is 30. Which means that using extraordinary means you CAN push your stats beyond 20, but never over 30. Even gods such and Tiamat and Bahamut have their stats maxing at 30.

the books go past 30

yes

it says health and diet tips. for those commenting on races like warforged/vampires - how would this help them? 

I usually use 6 to 10 seconds depending on if it is just for battle or if it is for survival foraging and stuff. 6 for battle kind of game and 10 for survival foraging kind of game.

Quote from Jaeger_Grayshield >>

Could a creature benefit from the same manual more than once? Seeing as certain races live past centuries, they could in theory reuse such a book again and again

In theory, I would say maybe. You aren't learning anything new but the magic in the book should still work. Personally I would say no as other magic doesn't stack in RAW and you should know the info from the book.

In the end it is up to the Game Master and their setting. 

Quote from Smartbutterfly4 >>

NOTE: JUST FOUND OUT EVERY TURN ISN'T A HOUR I search and search some say 6 seconds some say 10 minutes Idk tbh I'm confused lmao

 A turn is 6 seconds