a few recent books about Vietnam are being avidly read around the Pentagon and West Wing, including Lessons in Disaster by Gordon Goldstein and A Better War by Lewis Sorley.
I have a better suggestion: Jungle of Snakes by James Arnold. Arnold looks not only at Vietnam, but three other counterinsurgency wars of the 20th century: the U.S. in the Phillippines at the beginning of the century; the British in Malaysia following World War II; the French in Algeria; and the U.S. in Vietnam. The first two of these were successful campaigns that defeated insurgencies, the second two were failures.
As many observers have pointed out, Afghanistan is different from Vietnam in many ways. Nor is it exactly like the other conflicts I just mentioned. But all counterinsurgencies have features in common, as Arnold's work makes clear--for instance, any counterinsurgency must begin by assuring security of the civilian population; the success of any campaign depends on quality intelligence; and no counterinsurgency can succeed in the absence of a central government that earns the population's trust.
Rather than obsessing over Vietnam--admittedly, the most painful wound in the nation's military psyche--our strategists might profitably expand their data pool by considering what has worked, or failed to work, in other settings as well. Arnold, a veteran military historian, crisply and dramatically conveys what it was like for American boys plunked down in a Phillippine jungle, or French officers trying to tell friend from foe in Algiers (where, disastrously, they resorted to torture). And he steps back to sort out some key principles that any commander facing outlaws and guerrillas needs to know. I recommend Jungle of Snakes to anyone who wants to understand the kind of "asymmetric conflict" our nation is likely to be involved in for the foreseeable future.