Two Complete Science-Adventure Books was a Pulp published by Wings Publishing Co. from 1950 to 1954. Most SF novels are short (about 60,000 words) at this time so two nicely fit in one package. The publishers also did a detective novel version. (Real Adventure Publications had been doing this with Mystery novels since at least 1943. There were Western pulps of this sort in the 1940s as well.) Allen Anderson did the covers for the series from 1950-1952. Frank Kelly Freas did 1953-1954.
The idea of putting two SF novels together might have been part of what inspired Donald A. Wollheim and ACE Books to create the ACE Double for Science Fiction in 1952. (ACE did this with detective and Western novels too.) That company continued the practice until 1981. ACE Books’ move may have killed the Pulp but by 1954 all the Pulps were dying. The future was in paperbacks.
The first editor of TCSAB was Jerome Bixby of “It’s a Good Life” fame. His selections for the series were an interesting mix of classic authors and less prominent and often older authors. (The oldest book is The Time Machine (1896). Bixby was followed by Malcolm Reiss in the Winter 1951 until 1953. Katherine Daffron would edit the last two issues. All the editors selected novels with some action as the magazines title implies “adventure”. Some of the choices were destined to become classics while others are forgotten Pulp. L. Sprague de Camp’s The Tritonian Ring is unusual since it is a Sword & Sorcery novel and not even close to SF. It does have a John W. Campbell/Unknown feel to it though.
1950
Pebble in the Sky by Isaac Asimov/Kingslayer by L. Ron Hubbard (Winter 1950)
1951
The Star-Kings by Edmond Hamilton/Secret of the Sphinx by Arthur C. Clarke (Spring 1951)
The Sword of Xota by James Blish/The Citadel in Space by Neil R. Jones (Summer 1951)
The Time Machine by H. G. Wells/The Tritonian Ring by L. Sprague de Camp (Winter 1951)
1952
The Humanoids by Jack Williamson/The Outcasts of Venus by Anaximander Powell (Spring 1952)
The Cructars Are Coming by Paul Lawrence Payne/Minions of the Moon by William Gray Beyer (Summer 1952)
Beyond This Horizon by Anson MacDonald (Robert A. Heinlein)/The Magellanics by Alfred Coppel (Winter 1952)
1953
Sargasso of Lost Cities by James Blish/Survivor of Mars by Vargo Statten (John Russell Fearn) (Spring 1953)
The Wanton of Argus by Kilian Houston Brunner (John Brunner)/Mission to Marakee by Bryan Berry (Summer 1953)
Silent Victory by Poul Anderson/Ballroom of the Skies by John D. MacDonald (Winter 1953)
1954
Tombot! by Don Wilcox/World Held Captive by Bryan Berry (Spring 1954)
Unlike the ACE Doubles, Two Complete Science-Adventure Books had interior artwork. Look and artist choice is standard Planet Stories, which Malcolm Reiss, Paul L. Payne and Jerome Bixby also worked on. Artists included Paul Orban, Herman Vestal and Frank Kelly Freas.
Artist Unknown