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.
I've had this book a few days and these are a hard selection of puzzles. There are 5 levels of difficulty and I'm having difficulties with the first level puzzles. I dont consider myself a Sudoku expert solver personally, but I do have a spreadsheet I designed which quickly pinpoints 'singletons' (apparently equivalent to the first iteration of solving methods of all computer Sudoku solvers) but the starter problems all required an extra level of logic to solve. It comes in a handy size and at 2 pence per puzzle it must be good value for money for all Sudoku buffs looking for a harder selection of puzzles to solve.