Astral projection, mana manipulation, greater pass (allowing you to bypass magical defences, but that could also just be implemented as a regular upgrade to said spell), resurrection spell could lead to some interesting story progressions, a charm for demonic beings.
And im just brainstorming here but, a create life spell, enabling you to conjure a person, and this together with the transform spell for all kinds of customization... you get the idea.
Morph spell allowing you to transform in to someone else( could also be implemented as just an extension of the already existing transform spell)
A summoning spell.
Would be nice if at one point the protagonist starts generating mana naturally hinting his transformation in to a full on warlock.
A mind reading spell, ( could also be just an extension of clairvoyance)
Thats pretty much all I can cook up at the moment but what I would like to add is, perhaps you could add another magical book in the game that contains the non mind and body manipulation spells, and keep the book of control about , well control...
The other book would focus on demonology stuff and and defensive offensive spells incase at some point you decide to expand the game in to the demonic realm , for example we could travel through the hell gate instead of closing it and expand the story there.
Or to avoid complications to this, add more pages to the book of control, first page focusing on charms dai chu ,unlife demonic charm and whatever you choose to add.
second page focusing on means of travel, transport , pass , possession(because you are technically traveling to another body)
And 3rd for offensive defensive and just plain useful spells like clairvoyance invisibility , mana manipulation... or something...
And 4th for transform, resurrection, conjuring and all those sorts of spells that manipulate the flesh in some way.
And thats just if you want to categorize things. You could just make a page in the book for each spell and also list the upgrades to those spells on same page.
That way you are not setting any limit to yourself and can add whatever you like whenever you feel like it and keep the whole thing looking neat.
I hope that was helpful, anyway, whatever you decide to do great game and keep it up.