The item looks the same as other spell-books, but it's colored green.
When used, large vines will form from the floor below nearby enemies, immobilizing them.
The Vines will last some time and then collapse.
While the monster is affected it can't move, or turn around. This is a really good way of killing monsters since you can then go behind them and hit them on the back. It is most effective in a co-op game as one player stop can the monsters and another slays them.
Caution is advised, if the monster sees you it will attack the Vines in order to break free. Low-level monsters will need more attacks to destroy the vines, but it will take high-level monsters only one or two attacks.
Also, the Vines are destroyed when a player hits them so you have to be careful when attacking rooted monsters.
An interesting faculty of the Vines tome is that it affects any living statue nearby (guardian) even if you have not awoken it, so it can be used to detect hostile guardian's.