"Legend" by Edward J. Epstein has got to be right up there for me.
Although he doesn't say (maybe because James Angleton was still alive?), Epstein's sources appear to have been my pro-Golitsyn, anti-Nosenko heroes Angleton, Tennent H. Bagley, Newton "Scotty" Miler, William Hood, and William Sullivan.
Another book that appears to have some "pearls" in it is "The Man Who Knew Too Much" by Richard Russell.
-- MWT