Short version: two-fisted hero type goes to alien planet, has Golden Age pulp science fiction adventures. Does it all. Goes back home, nobody believes him, gets used to that. Forty years pass. Then they need him again…
Ate it in one gulp: Mark Millar wrote a nice thing here that played it exquisitely straight. Glad to have it in my library: and if the cover below appeals to you, you probably will too. Check it out.
Hmm, kind of sounds like Leigh Brackett’s Star Kings novels, from the fifties or sixties I think.
Looks interesting. I’m going to give this a try.