while the author's approach to proofs is refreshingly logical, he takes away from the wholeness of his work by including ONLY odd-numbered answers. his first edition had all of the answers to all of the questions. most students of mathematics are self-taught and highly motivated. with the exclusion of even- numbered answers, the author has saved a few pages and a bit of work.i feel fortunate to have a copy of the first addition which i purchased at a used book store for a buck. you can't beat that! :-)