In the Field, Among the Feathered is a history of North American bird field guides, from Birds through an Opera Glass in 1889 through the present day. It presents a fairly thorough examination of field guides (along with some other books, such as Silent Spring, Wild America, and Kingbird Highway) up to the last decade or so. Unfortunately, like most histories, treatment of recent works is frustratingly brief. Many recent books are discussed, but none are treated in detail.
The biggest surprise to me is that he refers to the most recent stage in field guide evolution as the "environmental" period. Dunlap argues that modern bird guides, by providing a framework enabling the pastime of birding, encourage the appreciation of nature. Further, by enabling amateurs to identify birds with ever-greater skill, they allow birders to serve as citizen scientists whose observations greatly aide conservation agencies.
This is quite the opposite of what Spencer Schaffner argues in Binocular Vision. I tend to lean more toward Dunlap's position, but I think he argues just a little too strongly that today's books and listing-oriented birders are "environmental". For instance, I'm not convinced that “competition increased consciousness about birds and about human threats to them”, as the author writes.
Still, as an exploration of the history of field guides, In the Field, Among the Feathered, despite a few shortcomings, is worth reading by anyone interested in these books.
Here's my full review of In the Field, Among the Feathered