Love these puzzles!  My son enjoys them and they are great to encourage logical thinking.  We have most of the Perplexors in the series, check the others out.  Great for gifted learners.  My only complaint is the book is thin, so not too many puzzles and they can be gone through quickly.  I have just scanned the puzzles and reprinted them at a later date so my son can work the puzzle again.  Of course with enough time in-between so he doesn't remember the answers.  I highly recommend these!