As I've published two ebooks of fiction in consecutive months, you may be asking how ex-Marine sniper Tom Gregory (First In, Last Out) differs from 1930s aviator C.J. Stone (Stones).
The Gregory stories are contemporary; the Stone stories are period.
Tom Gregory is a loner before and after the Marine Corps; C.J. Stone loves to tell and hear stories.
The Gregory stories are third-person action; the Stone stories are driven by C.J.'s unreliable narration.
I think the books have different audiences, but I'd gladly hear from readers who enjoy both.