I my opinion useless since the book won't stay open on piano stand.
I tried to return it, but the return was refused since notebooks are not covered by 30 day money-back guarantee. However, it is not said in the guarantee that notes are not covered.
Extremely disappointed.
I will probably try to cut off the binding and rebind the book with a plastic binding comb.
As for the arrangements, the difficulty level is in general quite challenging, it is rare to find a piece not requiring both hands playing quavers and/or 2/3 simultaneous keys for most part of the piece.
The overall feeling of the book is very sterile, no graphics, no introduction of pieces.