Introduction to Photographic Theory
The Photographer's Eye - John Szarkowski (ucd library link)
The Nature of Photographs - Stephen Shore (ucd library link)
The Genius of Photography - Gerry Badger (book plus BBC Documentary Series) (ucd library link)
Camera Lucida - Roland Barthes (ucd library link)
On Photography - Susan Sontag (ucd library link)
Ways of Seeing - John Berger (ucd library link)
The Ongoing Moment - Geoff Dyer

Walker Evans & The Photograph as Document
American Photographs - Walker Evans - texts by Lincoln Kirstein (ucd library link)
Walker Evans: The Hungry Eye - Gilles Mora & John T.Hill (ucd library link)
Atget - John Szarkowski
Changing New York - Berenice Abbott, Bonnie Yochelson (ucd library link)

The City
Silver Cities:photographing American Urbanization 1839-1939 - Peter Bacon Hales (ucd library link)

The Street
Bystander: A History of Street Photography - Joel Meyerowitz & Colin Westerbeck - ch. 17-Klein & ch. 18 - Robert Frank are particularly important (ucd library link
Life is Good and Good for you in New York: Trance Witness Revels - William Klein (ucd library link)
A Way of Seeing - Helen Levitt, with forward by James Agee
The Man in the Crowd - Garry Winogrand

The Road
The Americans - Robert Frank, introduction by Jack Kerouac (ucd library link)
Uncommon Places Stephen Shore (ucd library link)
Interview with Stephen Shore - Aaron Schuman for Seesaw Magazine
Accounting for Days: Lynn Tillman on Stephen Shore's Roadtrip Journal - ArtForum, Summer 2007

The Landscape
American Prospects - Joel Sternfeld, Andy Grundberg, Katy Siegal
Crimes and Splendours: The Desert Cantos of Richard Misrach - Richard Misrach and Rebecca Solnit
Perpetual Mirage: Photographic Narratives of the American West - May Castleberry

AddAllA good book-finding site