This has certainly been making the rounds but I wanted to make sure it was brought up here. Deep Magic, a Pathfinder spellbook from the wonderful folks at Kobold Press.
Originally this started as a compilation of seven years of Kobold Press magic material, but it's been a monster success and exploded with stretch goals: new schools of magic and archetypes and other weirdness from some of the best. And there is apparently much more to come if folks continue getting on board.
All the remaining pledge slots for hardcover copies are relatively expensive at this point, but $25 will get you a pretty bonkers PDF. Check it out.
If the demon and angel magic unlocks, vril is also interesting.