vntg 1957 Frank Belknap Long ACED-544 SPACE and similar items

Previously released by ACE in their back to back omnibus format, ACE says the standalone book was released in 1962 with the same cover art (per ISFDB). Tight, flat, square book. Edge wear, wrappers creased, scuffed. Spine creased, scuffed and chipped. Pencil marks on the FFEP. The Space Station floated up out of the Big Dark. Lieutenant Corriston had come to see its marvels, but he soon found himself trapped in unexpected terrors. The grim reality was that an unknown, unsuspected outer space power had usurped control of the artificial moon. A beautiful woman had disappeared; passengers were being fleeced and enslaved; and, using fantastic disguises, imposters from - SOMEWHERE - were using the station for their own mysterious ends.