Oh OK.

No. Since you attached the hammer to the Book, you can only bring it into play using the special rules of the Book.

You can't just take it off arbitrarily.

The +2 ark is good and all, but would it not be better to equip someone with a hammer that gives them abilities they don't already have, rather than abilities they already have?

That would depend on who else I would have on my team.

Or if you want them to have ability's that can't be outwitted.