Two sets with six books in each set. Each is 4-1/8x6-7/8" with page count ranging from 160 to 202. First five Avon titles are copyright 1974 and last title is copyright 1975. All are based on creator Alex Raymond's original story. All feature wonderful George Wilson covers with Alex Raymond art on back covers. Titles include: The Lion Men of Mongo, The Plaque of Sound, The Space Circus, The Time Trap of Ming XIII, The Witch Queen of Mongo, The War of the Cybernauts. Second, third and fourth titles each have small price sticker on front cover. A few tiny color rubs here and there but overall group is VF/Exc. First three Ace Tempo titles are copyright 1980, last three are copyright 1981. Number one through four feature front cover art by Boris Vallejo. Titles include: Massacre in the 22nd Century, War of the Citadels, Crisis on Citadel II, Forces From The Federation, Citadels Under Attack, Citadels on Earth. Fourth and sixth titles have price sticker on front cover, a few tiny color rubs here and there on covers but overall set is VF/Exc. An instant Flash library with superb cover graphics.