I'm reading a recent book about the first decade of US involvement in Vietnam (i.e. 1954-1965). It's a "revisionist" work and it's quite good.
http://www.amazon.com/Triumph-Forsak.../dp/0521869110
Moyar challenges many of the widely accepted notions about America's involvement and South Vietnam's political and military potential in particular. Moyar's research seems exhaustive. He uses a great deal of primary documents including a great deal of VC/NVA material that, IMO, makes for a solid case. For example, the South Vietnamese military's early counter insurgency efforts were regarded as lackluster by the 1970s but the contemporary evidence tells a mjuch different story. I would recommend this to anyone interested in the Vietnam War.