Ive spent a long time perfecting this subclass trying to make it balanced and take on a niche of its own. It would be much appreciated for some feedback.

Warlock Subclass: Arcane Codex

Wield the Mysterious Power of Arcane Scripture

Your patron's power takes the form of a Codex: a tome, scroll, or sheaf of parchment inscribed with living script. Its symbols awaken at your command, shaping themselves into wards that turn aside blows meant for you and for those who stand beside you.

Level 3: Arcane Codex Spells

The knowledge in your Codex ensures you always have certain spells at the ready. When you reach a Warlock level specified in the Arcane Codex Spells table, you have the listed spells prepared. These spells don't count against the number of spells you can prepare.

Arcane Codex Spells

Level 3: Script of Protection

Pages of glowing script tear free from your Codex and orbit you in a protective ring.

Activation. As a Bonus Action, you can activate Script of Protection if you aren't wearing armor or wielding a Shield. It lasts for 1 minute.

Floating Pages. When you activate this feature, a number of magical pages emerge from your Codex and orbit you, as shown in the Floating Pages column of the Arcane Codex table. While you have any floating pages remaining, your Armor Class increases by 1 for each page active.

Sacrificial Burn. When you are hit by an attack roll while you have at least one floating page, you can take a Reaction to expend one of them. You gain a +5 bonus to AC against the triggering attack, potentially causing it to miss. The expended page burns away, which reduces the AC bonus from your floating pages by 1. An expended page can't be recovered during that activation.

Ending the Script. Script of Protection ends early if you have no floating pages remaining, if you have the Incapacitated condition, or if you don armor or wield a Shield.

Limited Use. You can activate Script of Protection a number of times equal to your Charisma modifier (minimum of once). You regain all expended uses when you finish a Long Rest.

You have 3 pages 

Level 6: Intercessory Script

You can extend the Codex's protection to your allies.

Expanded Protection. While Script of Protection is active, you can use Sacrificial Burn when a creature you can see within 30 feet of you is hit by an attack roll. If you do, that creature gains the +5 bonus to AC against the triggering attack instead of you. The page burns away as normal.

Greater Script: Your pages increase by one page to a max of 4 pages.

Level 10: Chapter of Endurance

Your long bond with the Codex has hardened your body against harm.

Enduring Scholar. You gain the Tough feat.

Greater Script: Your pages increase by one page to a max of 5 pages.

Level 14: Mantle of the Arcane Codex

You can call on the Codex's deepest wards, wrapping yourself in a pale-blue mantle of arcane energy. While Script of Protection is active, you gain the following benefits:

Arcane Fortitude. You have Advantage on Constitution saving throws.

Arcane Resistance. When you activate Script of Protection, choose Cold, Fire, Necrotic, or Poison damage. You have Resistance to the chosen damage type until the script ends. You can choose a different type each time you activate the feature.

Greater Script: Your pages increase by two pages to a max of 7 pages

Arcane Codex

I think this subclass is very interesting mechanically, but there are a couple things I'm not sold on.

1: What exactly is the flavor of this? Is the Codex sentient? How does a warlock form a pact with a book? The flavor feels far more wizard-like than warlockey.

2: Why is every single feature defensive? The 3rd-level feature is very cool and descriptive, but the problem is that it doesn't do anything if you aren't getting targeted by attacks. This critique applies to all of the features, especially the 10th-level. I would be really disappointed if I hit level 10 and my only reward was more HP. Let this subclass do something cool, like blind enemies with swarms of pages or something similar. 

This is a very interesting concept, but all of the features after the 3rd level ones are rather boring. It also seems quite underpowered. I would suggest revising the features to be more powerful and more interesting or unique. Getting an Origin feat at 10th level is not good.

This is the skeleton of the subclass. The flavor I'm aiming for is CC AoE and single target CC. I wanted to give players the freedom to flavor The Arcane Codex the way they want to. 

The original concept was this:

A powerful Githzerai Wizard, was obsessed with immortality. He thought researching the echoes of the planes could lead to a brakethrew. Over centuries he built his knowledge made impossible discoveries, and found ways to prolong his life, but death always wins. On his death bed he casts his final spell onto his grimoire The Arcane Codex. It transferred his mind, soul, and conscious into the Book. Any that holds the Codex in which It thought was worthy of his knowledge and power could gain its favor. 

Over time, it passed from one hand to another. The Codex learned from each. All implementing more complicated and powerful magic on to its pages. All for one day, hoping he could free himself from his Codex and become more than just a book.  

It is kind of wizardry because the source of the power is an incredibly powerful wizard.  

Why defensive? Because I wanted to create a truly defensive subclass.

The 3rd level you can protect yourself if you yourself are targeted but at level 6 you can protect your allies as well. 

As for unique abilities I need to keep it as clean as possible. Before when I originally made this subclass there was summons from the book. It would be A Summon Construct. It would be a creatures made from torn pages. This creature comes from the void of the planes. This creature would be a manifestation of rage, sorrow, and pain itself. You could use a bonus action to control it while you're sitting in the backline using CC on other monsters. 

Another Idea would be to use a burn on the page to have it attack causing 1d4 fire and 1d4 force damage. but I'd have to create a homebrew spell for that, and I want to try and keep it as clean as possible. 

I could work the Construct back into the build, so you have a powerful creature to control. 

If you have any more ideas let me know. Thanks for your reply.

The problem is that you have not made a subclass focused on CC. If you want crowd control, I highly recommend replacing either the 6th or 10th level feature with something similar to this:

Level 6 (or 10): Swarm of Pages

As an action, you can fill a 30-foot Emanation around yourself with swirling shreds of paper and pages from the Codex. Each creature of your choice that starts its turn in the Emanation must succeed on a Constitution saving throw or be blinded and have its speed halved until the start of your next turn. This Emanation lasts for 1 minute or until you lose concentration (as if concentrating on a spell).

Once you use this ability, you can't do so again until you finish a short or long rest.

This was not made with any attempt at balance, just an ability I thought would be cool for the CC focus you want.

I realy like this. I think what I’m going to do is bring the feat to the level 6 so you get that little extra HP and make 10 a good CC like you gave me. I realy do like that!