There are different colors on the wolf-model you get when using this book. The colors are red, white, black, or grey. Each book has its "own color"; it will transform the player into the same model each time. The model a book is able to give is chosen randomly when the book is made. The color of the model a book is able to give is written in the Use:-text (for example: "Transform into a giant white wolf.").
The buff has a 2-minute duration.
When transformed, you are pacified and silenced. You can, however, still do things like using or creating items.
Even though the books give different colors, they all share the same cooldown.
If you are transformed and un-equip the book, the buff will be dispelled.
There are several items with similar effects, some easier to obtain than others.