On some notes:
- Book of Spells turns the warlock into a full spells prepped caster because you can return it and borrow it again with two new spells. Is this intentional? (Likewise the book of Skills gives you access to all skills just as long as you don't need them all at once)
- Book of Skills + Pact of Knowledge feels like a ridiculous combo
- You're overlapping hard with the Pact Boons
- Book of the Mage is a Pact of the Tome-alike
- Book of War does what a lot of people (IMO rightly) make Pact of the Blade do and feels ... off ... for the theme
And does the expanded spell list also grab cleric, paladin, druid, and ranger spells for you?
Finally, although they technically know fewer spells the warlock isn't as strapped for spells known as the sorcerer because they aren't trying to spread the spells out over multiple levels.