I am always on the train or on long coach journeys going between uni and home at weekends, so I brought this to keep me occupied! But I now I seem to play it all the time wherever I am. If I've got my laptop with me I'll play on the computer or otherwise I carry the book around in my bag with me. I absolutely love solving the hard puzzles - even if it does take me way longer than the target time! I try to do them without any help but sometimes I just have to get the answers for the odd one or two squares or turn on the pencil marks! I've tried a few devilish puzzles but I still need to get better at the hard ones first! This is a great set for any sudoku fan and will last a lifetime! When I do eventually finish the book - I'll just print out puzzles from the software seen as though there are endless amounts! This is an absolute must!!