What is urban design? Is it a profession? a set of practices? the conceptual stuff that binds together architecture, urban planning, and landscape architecture? Consensus apears to be elusive.
For a readable overview of the discipline, see Urban Design, by Jonathan Barnett and Gary Hack, Chapter 13 in The Practice of Local Government Planning, 3rd ed., 2000, pp.307-340. In addition, a sampling of classic and contemporary readings in urban design is offered in 2 recent compilations of similar title:
The Urban design reader, Elizabeth MacDonald and Michael Larice, eds.
Urban design reader, Matthew Carmona and Steve Tiesdell, eds.
With only about 20% overlap in selections, both are worth perusing.