Raymond Smullyan introduces the readers to simple logic problems and then starts to grow them more complex. Answers to the puzzles are provided with explaination, but Smullyan's more recent books clearly dig deeper. However, if you want some good knight/knave and dracula puzzles, this is a good place to start to learn about Godel. I recommend also obtaining: "Lady or the Tiger? And Other Logic Puzzles Including a Mathematical Novel That Features Godel's Great Discovery"
About the Author
Raymond Smullyan, well-known mathematician and logician, is Oscar Ewing Professor of Philosophy Emeritus at Indiana University and Professor Emeritus at the City University of New York-Lehman College and ' Graduate Center. His many writings include six previous volumes of recreational logic and math problems, What Is the Name of This Book? The Lady or the Tiger" Alice in Puzzleland, To Mock a Mockingbird, Forever Undecided, and Satan, Cantor, and Infinity; two studies of deductive logic in chess, The Chess Mysteries of Sherlock Holmes and The Chess Mysteries of the Arabian Knights; and three collections of philosophical essays and aphorisms, The Tao Is Silent, This Book Needs No Title, and 5000 B. C.