A while ago I purchased Marine Mammals of the World: A Comprehensive Guide to Their Identification by Thomas A. Jefferson, Marc A. Webber, and Robert Pitman. It is an outstanding book, probably the best on Earth for Marine Mammals. It even has manatees and Polar Bears! Really the only reason I bought it (yes, I bought it, not my parents) was because of the Vaquita entry. It has great pictures and reliable information, and the best Vaquita illustration I’ve ever seen in a book. I’m not really asking you to buy it, but if you’re into marine mammals, it’s certainly worth every penny. It would also make a great holiday gift.
Marine Mammals of the World: A Comprehensive Guide to Their Indentification