After a disconnected array of logic puzzles at the beginning, the author embarks on an introductory course to combinatory logic. Given a little application (if you're like me you will need a pen and paper), you can get to grips with some of the fundamentals of mathematical logic with relatively little background. This is pretty astonishing.

The worst feature of the book is the fact that only one (unintuitive) model for the theory is provided. Discussion of the significance of the results obtained is not particularly useful - probably anyone smart enough to solve the puzzles will not find anything there that they couldn't figure out for themselves.

But nevermind: if you want a good introductory course in combinatory logic (or you want to understand (a version of) Godel's 1st incompleteness theorem), then I would recommend this book for you!