Here's a few covers from some of the long line of narrative Flash Gordon books that weren't comic strip focused. There were at least three periods in which novels were released. These are from the last series published by Tempo Books and written by David Hagberg.
I've not read these, but fellow space ranger Chris Mills posted over at Space1970 about picking a few and briefly mentioned that they follow more in line with the 1950s TV Flash, than Alex Raymond's interpretation.
I prefer my Flash caped with sword AND pistol, but these are pretty cool too!