For my custom games, I tried to use the Spell Book ability to make cool items like spell books and bags of trinkets. Unfortunately, there is a bug with the spell book ability. If I assigned a Spell Book Ability to a Spell Book Item, when the hero picked up the item, it would go into the first available inventory slot. Once in that slot, it would only work from that slot; using the item without moving it will bring up the spell options for the ability just fine. If the hero moved the item to a different slot, the item would no longer work and casting it would not bring up the available abilities. It works fine as a unit or hero ability as the ability cannot be moved so there is no such bug (that I could find). Unfortunately, I cannot make a spell book item (or an item with a spellbook ability) unless it is a campaign item and cannot be moved or dropped.
I’d like to see this bug fixed so I can make non-campaign items like a Ward Bag or a Book of Flame. It is interesting because you can have the Spell Book Ability share the cooldown of whatever spells are used, so one must decide whether to use a low cooldown ability to get the cooldown for the Spell Book Ability back faster for another cast or to use a higher cooldown ability for the damage or utility.