As the other reviewer said, this is an excellent book. Smullyan's style is engaging and entertaining. The riddles are excellent, and follow a learning curve that means you can actually learn to cope with them as you go through the book (well, so long as you have a mind for these things, I guess). From the first puzzle (two roads, 1 leads to safety and the other one to death, a knave and a knight, 1 question) to the last (count dracula's castle, filled with crazy and sane vampires, humans and other assorted logical monsters, 3 questions to find out if dracula's alive), you will learn to progressively twist your mind further and further out of shape until your friends kick you out of the pub for throwing one too many fiendish puzzle at them!