Photography Visionaries, published by Laurence King, is similar to Taschen's Photographers A-Z, and both have their strengths and weaknesses. Photographers A-Z is more substantial (a hefty volume profiling 400 photographers), though its illustrations are rather small. Photography Visionaries is more selective, though it includes many full-page images. Photographers A-Z contains detailed individual bibliographies, while Photography Visionaries features concise essays explaining the significance of each photographer.
Mary Warner Marien, author of Photography Visionaries, also wrote Photography: A Cultural History (arguably the best general history of photography) and 100 Ideas That Changed Photography. The Photography Book, by Ian Jeffrey, is another A-Z of photographers, with each represented by a single photograph. The first history of the art of photography was Beaumont Newhall's The History Of Photography, and Naomi Rosenblum's A World History Of Photography is a more recent example. The Focal Encyclopedia Of Photography is a comprehensive reference.