I was testing the new updated 6.5.0 MCCC mod, I was having the same problem with spell book wouldn't open and corrupted saves.. also, cheating the systems like adding points or using traits.equip_trait trait_Occult_WitchOccult_BloodlineWeak or any of this could corrupt the save or glitch the spell book from opening, and leveling panel glitch on the bottom of needs. this person also gave a warning
https://sims-online.com/sims-4-realm-of-magic-cheats-spellcaster-witch/ will break your game.. it did to me.. I remove MCCC and don't cheat the systems, remove any cache files and game is working as it should... I'm not saying is a fix for all the bugs.
