I couldn't finish 'em. Looks like this's gonna get complicated.
The weak spot of the Libroarian is the face, which is covered by a mask. He has powerful magic spell attacks (Quake, Slow, and Bio), but his ring is relatively slow and easy to get away from. He also has a quick slash attack, a ram attack and a long-radius ram attack, as well as a heavy jump to knock the player away (and off his head). He may also throw the magic books found in the library.
There are three ways to stun him. The most easiest is to use a Holy spell (stack a Cure and a Raise). However, he will recover quicker from Holy spells than over methods of stunning. The second way is to wait near a wall, and try and lure him to use the long-radius ram attack. He will hit the wall and be knocked out. It is harder to get to his head this way, due to his front facing the wall and being unreachable.
The last method is to use a magic book. He may throw these at the player, so try and lure him to do so by waiting out of his reach. If the player does not get hit by the book, they can pick it up and throw it on the tome. The magic will self-target Libroarian. If the player does get hit by the book, they will be stunned and the book will disappear.
If Libroarian casts magic, the player can double-jump onto his head and snatch the book, but this is rather unreliable, as the player may not always get the book. This is the only way in the battle to get a white book (ones that cast magic that follows the player or their magic ring).