When reading through this three-volume set, one gets the feeling that the author set out to write the definitive textbook for ornithology. In my estimation, Ritchison has succeeded in doing so: I expect this set—although hefty, coming in at over 2500 total pages—to be the go-to books for questions about birds. These volumes are comprehensive, thorough, and detailed. Although I read through them cover to cover (over several months’ time), I would guess the primary uses of these book would be: to serve as a reference for graduate students, postdoctoral researchers, and faculty studying anything ornithology-related; for undergraduates taking an ornithology class; and for the extremely enthusiastic and dedicated amateur birder or amateur biologist who simply wants to learn more about birds. I certainly intend to have this set front and center in my office bookcase, and anticipate using it regularly, for my own queries as well as that of my graduate and undergraduate students.>/p> There are 19 chapters split among three volumes and beginning, naturally, with the evolution of birds (speaking as an evolutionary biologist). The text then delves into different aspects of bird anatomy and physiology, highlighting the defining characteristics of the class Aves—which is also where the books get their play-on-words title. Crucially, these volumes are about the form and function of birds—as indicted in the title—so the emphasis here is very much on the anatomy and physiology of birds. That is why “integuments” gets its own chapter, roughly the same amount of space given to “origin and evolution.” Just as crucially, I think it is important to realize what this set of books did not mean to cover, and thus is not present, which is the evolution and ecology of birds. Some of the chapters touch on these aspects of birds, and indeed it is hard to fully separate bird form and function from ecology and evolution but, on the whole, these volumes are about bird bodies, and they do a wonderful, detailed, and thorough job on this. The set ends with five chapters on avian reproductive systems and strategies. These chapters comprise a large part of the text. This perhaps is not surprising, given that ornithologists have placed substantial emphasis on the breeding season biology of birds. For those less interested in breeding biology, it can seem like overkill. But much of what we know about mating systems, adaptive reproductive strategies, signaling, sexual selection, and behavioral ecology more generally comes from studies on birds. In addition, because of ornithologists’ focus on breeding biology, there is simply a lot of information on these topics. Thus, the intensive focus on this aspect of bird biology, and the role bird studies have played in illuminating some of the fundamental ideas in evolution and ecology, makes sense to me. One of the aspects of these volumes I especially appreciated is the clear figures and photographs. The illustrations and figures throughout were well chosen, and one can get lost in the intricate and cool images—the bird eyeballs, the sets of penguin tongues, the matching of avian genitalia, and the heat map of a chick. For me personally, avian physiology and anatomy are not my strong suits, so these volumes have been very helpful. In this world of quick (but possibly incorrect and AI-generated) online answers, often with little or no context, I have enjoyed using these books as important reference guides. I think it can be very personal what parts of these volumes will be of most interest to someone, and I would suspect it will be the things you know the least about. I found the chapters on digestion, flight, and the respiratory system particularly fascinating, but that is likely because I know very little about these topics. Conversely, on evolution and mating strategies, I did not learn much that was new to me. As with any volumes that have this kind of all-encompassing scope, the difficulty is more in figuring out what to include and highlight, and what to leave out, as well as how to condense the enormous amount of data, results, and studies into the main ideas for readers. I think the author has been successful in this endeavor—I finished reading these volumes thinking they had broadly covered all of the topics I would want a graduate student to understand about bird bodies, and provided enough information for students to pursue further knowledge. Ultimately, this is a tour de force. Like The Sibley Guide to Birds and the Handbook of the Birds of the World, I think this publication belongs in every ornithologist’s office. It is an impressive work, and what I think of as a gift from Ritchison to our field.