@futurebird for more of a "human impact" side of the Vietnam War:
"The Things They Carried" by Tim O'Brien had a huge influence on me as a writer. I studied it in 11th grade English and again for my degree. He's written some other stuff but that's his most famous one.
"Achilles in Vietnam" and "Odysseus in America" by Jonathan Shay, a VA psychiatrist who works almost exclusively with Vietnam vets. These address political and bureaucratic factors besides combat