I would be amazed if someone in congress had any idea what books to read to help evaluate the current predicament.
Afghanistan and Vietnam are two different wars, different cultures and different beliefs. While it is easy and lazy to compare the two applying the same strategy would (will) not work.
To make it easy for them to understand, some light reading such as 'The Afghan Campaign' would help push them in the correct direction. Historical fiction that tells how Alexander contemplated and dealt with Afghans. Perhaps it would engage them enough to actually read it?