Spell mastery takes time. With Grimoire one must always have a spell tome on hand to cast its spell until mastery is achieved. What this means is that upon reading a tome you will learn the spell as usual. However, to equip the spell you must have the same spell tome in your inventory until the spell has been mastered. Each time you cast the spell, your mastery of it increases. The speed at which mastery increases is configurable in the provided MCM. By default, the spell must be cast 100 times before mastery is achieved.
Normally when reading a spell tome for the first time, it is consumed and removed from your inventory. By default this no longer happens with Grimoire, but that behavior can be restored from the MCM. Additionally, you can check the mastery status of any equipped spell in the MCM.
The Dragonborn and Dawnguard DLC are required, as well as SKSE.
All vanilla and DLC spell tomes are recognized in a form list (_JSW_G_SpellTomes). To facilitate the creation of patches for spell mods, this form list is checked for new entries and it is automatically updated in both a new game and when loading an existing save.