This note contains spoilers for the book.

Parker takes on the Tombstone story; the Earps, Doc Holliday, Ike Clanton, Bat Masterson, and the like. Also one "John Ringo", who I'm pretty sure is not the current SF/military author.

I gues maybe he wanted to write about somebody less talkative than Spenser?

It's in some degree a love story—Wyatt Earp meets and falls instantly in love with Josie. That's the basis of the real trouble he gets into in Tombstone; and Earp and Josie stay together for life.

This Wyatt Earp is the only wild west gunman I remember who practices.