I recently got a copy of Upstream: The Ascendance of American Conservatism by AmSpec's publisher Al Regnery and went to work on it.
First, if you are a conservative without much knowledge of the history of the movement, then you must read the book. You'll have a much richer appreciation of the battles that have been fought and why some of the fault lines are still there.
Second, the book is just fun to read. Regnery tells the story in an entertaining fashion and has interviewed many of the big names. SLIGHT SPOILER: Hubert Humphrey embraced conservatism before his death! Or, at least, so claimed Paul Laxalt in an interview with Regnery.
Upstream stands up nicely to other movement histories like George Nash's The Conservative Intellectual Movement in America since 1945 and Lee Edwards' The Conservative Revolution.