If you're interested in public art commissions, I suggest subscribing to Public Art Review. Here are some books that might also be of interest.
Tom Finkerperl, Dialogues in Public Art
Jeffrey Kastner, PLOP: Recent Projects from the Public Art Fund
Suzanne Lacy, Mapping the Terrain: New Genre Public Art
Malcolm Miles, Art Space and the City: Public Art and Urban
W.J.T. Mitchell, Art and the Public Sphere
Harriet F. Senie and Sally Webster. Critical Issues in Public Art: Content, Context, and Controversy