The Mucker and its sequel, Return of the Mucker, are E.R. Burroughs novels about the kind of guy who might be a third-class mook in some of his other novels. The Mucker is a thug from Chicago with no talents, no prospects, no education, and no morals.
Somehow he develops all of these after fighting degenerated headhunter samurai after being shipwrecked on a Pacific island along with a parcel of high society dudes including a beautiful and nervy girl who is good with a wakizashi. (Not making that up.)
The Return of the Mucker switches genres to Western, but I never got ahold of it to finish.