This 202-page paperback from Tempo Books, published in 1980, doesn’t carry any author credits at all, not even a mention of Alex Raymond as the character’s creator; a little research however reveals that David Hagberg wrote all six novels of this series published in 1980/1981.  Apart from a Terminator 3 tie-in and one 1982 novel, plus a couple of more recent short stories, that’s about all he has contributed to our field, though Wikipedia reveals that he is best known as the writer of a series of techno-thrillers starring Kirk McGarvey, after starting out doing “work for hire” on more than a score of “Nick Carter – Killmaster” novels.  The cover here is by Boris Vallejo.

“Sent on a mission to investigate the mysterious reappearance of the Interstellar Exploration ship GOODHOPE, Colonel Flash Gordon and his companions, Dale Arden and Dr. Hans Zarkov discover much more than they had bargained for.  Stranded in deep space, the trio find themselves drawn against their will into a war of worlds which has lasted thousands of years…and which threatens the very existence of the planet Earth.”

The five subsequent titles, War of the Citadels, Crisis on Citadel II, Forces From the Federation, Citadels Under Attack, and Citadels on Earth, would seem to suggest a continuing storyline; the books apparently have not been reprinted in the last thirty years.