it feels like we're perpetually on the verge of a tipping point, when e-books will overtake print books as a source of revenue for publishers. John B. Thompson, a sociologist at the University of Cambridge, analyzes the inner workings of the contemporary trade-publishing industry. (He did the same for scholarly publishing in an earlier work, Books in the Digital Age.) Mr. Thompson examines the roles played by agents, editors, and authors as well as differences among small, medium, and large publishing operations, and he probes under the surface of the great digital shift. We're too hung up on the form of the book, he argues: "A revolution has taken place in publishing, but it is a revolution in the process rather than a revolution in the product."