The puzzles are reasonably challenging even from the start, and the size of the book is very handy. This is helped by the answers being printed 12 puzzles to each page, thus the bulk of the pages are devoted to the puzzles, unlike with some other books where with two puzzle answers per page the answers occupy a third of the book. The puzzles are divided into five levels of difficulty, and being now about halfway through the book I am noticing the puzzles are getting more difficult. My complaint is with the quality of the paper used - rubbing out is quite difficult as the pencil lead buries itself deep into the paper fibres, and as a result of this and the poor strength of the paper some of the pages have torn during the rubbing out process.