I gather this guy isn’t another total fraud like Jack Coughlin, the guy who wrote ‘Shooter: The Autobiography of the Top-Ranked Marine Sniper’?
I don't know which "guy" you're talking about. If you doubt the bona fides of Chris Kyle, go read the article. Seems pretty genuine to me.
As to the other guy, Harold Wasdin was a member of SEAL Team Six and fought in the battle for Mogadishu. His book is very real and will curl your toenails.