One great recipe for science fiction romance includes a military setting/characters and a forbidden romance. That setup promises conflict, politics, and sexual tension of an epic nature.
We need a list! Here's the criteria: The story must be a military science fiction romance where at least one of the characters is in the military and the couple embarks on a forbidden romance. Here are the ones I immediately thought of:
THE OUTBACK STARS - Sandra McDonald
GAMES OF COMMAND - Linnea Sinclair
COLD WARRIORS - Clare Dargin
ENEMY WITHIN - Marcella Burnard
THE SPIRAL PATH - Lisa Paitz Spindler
SHARDS OF HONOR - Lois McMaster Bujold
PRIMARY INVERSION - Catherine Asaro
MOONSTRUCK - Susan Grant
REBEL SOULS - D.L. Jackson
Which titles would you add? I'll update the list accordingly.