Paul Humann's now out-of-print book is part of an easy-to-use, photo-illustrated series of fish and invertebrate identification books. Information is given to differentiate species, habitat and location, as well as sizes- and often, photos of different color / life phases are shown. Great for snorkellers and divers. Its replacement is not due until late 2003, and then it will cover Cocos and Malpelo Islands as well as the Galápagos Islands. When it arrives, I will undoubtedly give it my highest recommendation, with all the others in the series- well done, Paul and Ned!
For those who want a more in-depth tome, I recommend Jack Grove's "The Fishes of the Galapagos Islands" (Hard, 936 pages, 1.94" x 10.35" x 7.27" , Stanford University Press, 1997; ISBN 0804722897, cost US$130.00) - THE definitive Galápagos fish identification book for those desirous of more comprehensive information, but by its size and price, no lighweight field guide for novices.