Book Wyrms adds Book Wyrms to your forests, lizards that come in a variety of colors. You can herd them for their meat and colorful scales, using plain books to breed them. Most importantly, you can feed them unwanted enchanted books to recycle them into new random enchanted books.

Wyrms come in 7 colors, each with a different pool of enchantments they can provide:

Gray, most common, can produce any enchantment
Red, can produce enchantments for melee weapons like Swords
Orange, can produce enchantments for ranged weapons, like Bows or Crossbows
Green, can produce enchantments for tools, like Pickaxes or Shovels
Blue, can produce enchantments for armor or Shields
Teal, can produce enchantments for Fishing Rods and Tridents
Purple, can produce enchantments for some misc modded items like Domestication Innovation's Collar Tag (if none are present, they will act as Grays)

Additionally, Wyrms have various genes that affect their recycling behavior, which you can see using the Book Wyrm Analyzer:

Enchanting level, determines how many levels the Wyrm needs to digest before making a new book (stronger enchantments are worth more levels) and how strong are the enchantments it can produce
Digesting speed, determines how fast does the Wyrm digests books
Indigestion chance, determines how likely the Wyrm is to have an indigestion and regurgitate some shredded paper and (magical) digestive fluids

While the boluses produced by indigestion may feel bad, they can be refed to recover part of the magic of the digested books, or made into Wyrmutagen. This substance will let you modify the stats or color of your Wyrms. Changing a Wyrm's color will also cause it to shed its previous scales, letting you peacefully obtain more (even if you changed it to the same color).

Spotlight (outdated textures):

Current mod compatibility:

Any modded enchantment can be produced by Gray Wyrms, and also by the appropriate colored one if it's for a matching vanilla item (for example, Ars Nouveau's Mana Boost/Regen go on vanilla armor, and as such will automatically be added to the Blue pool if the mod is here)
Guns Without Roses's guns go in the Orange pool
Domestication Innovation's Collar Tag goes in the Purple pool
Alex's Mobs's Straddleboard goes in the Purple pool
Superior Shields's Shields go in the Purple pool
Create's Potato Cannon goes in the Orange pool, Copper Backtank in the Blue pool
I Wanna Skate's Skateboards go in the Purple pool
If Farmer's Delight is present, you can slice Wyrm meat just like you can slice other meats, and the Stews will require the Cooking Pot to be made
If Mekanism, Create, Thermal Expansion, or Integrated Dynamics is present, you can grind Scales into Dye using their machines
If Botania is present, you can cycle through the Scales' color using a Mana Pool and the Alchemy Catalyst

Configuration:

Natural spawns are done with a biome tag and a forge biome modifier, maybe a datapack/kubejs/crafttweaker can change them, let me know if that works
Stats of wild Wyrms, the stat caps, and how effective are the various Wyrmutagens can be changed in the common config
Enchantments that the various colored Wyrms can provide can be changed through the pool_<color> item tag (the enchantment pool is any enchantment that can be applied to at least one item in the tag, empty tag = default to all enchantments)
If you get reported about a "Suspicious Chad Bolus", it means that there are no enchantments for a given color pool at a given enchanting level, check the configs for ways to mitigate if necessary (it shouldn't happen in vanilla with unconfigured values, might come up with higher enchanted values, modified pools, or unlucky mod compat with the purple pool)