An exciting but at the same time troublesome book: without a doubt it is an up-to-date statement of our knowledge about the red planet, but far too little emphasis is placed on the speculative nature of some of that knowledge. In fact, because of the writer's style, it becomes difficult to Judge when one is reading fairly solid information and when merely the best available suppositions. Otherwise, it is an authoritative assessment of current information which becomes, at times, rather commercial in its implicit but positive support of the NASA line. Contents include photos, a glossary and a useful appendix of the recommendations of the National Academy of Sciences Space Board regarding the exploration of Mars. With the aforementioned reservations, it is still superior to many of the older books on Mars for the age group.