Spellcraft scrolls, which are different from normal scrolls like scrolls of light. To craft one, you need one of the one time use items. For example, dagger seal: might gives you might once and then goes away, but you can alternatively use it to craft the spellcraft scroll of might.
You can then gain the new spell by activating the spellcraft scroll and then waiting as your character stares at the symbols. You aren’t guaranteed to get the spell after using one scroll, so it is a good idea to make multiple.
You can also automatically gain spells when you go down the mod’s custom mutation paths.
tl;dr use spellcraft scrolls or go down the mod’s mutation paths.
Also, if you are annoyed with how the spells keep making you sleepy, just drink copious amounts of coffee and other stimulants. Sleep is for the weak.
