Moon Base by E.C. Tubb
Paperback – Ace – 1964
“Felix Larsen had been sent to Luna Station One to investigate ‘something odd on the Moon.’ There was no proof, not even a concrete basis for suspicion, yet there was a feeling so wrong about the place that Security had hinted of traitors.
On the first day at the sealed station beneath the Moon’s crust, Felix had become violently ill. He awoke from a drugged sleep with no memory of the intervening time lapse. Now he had to be doubly careful because his secret might be out, and somewhere in the station — or somewhere out there on the alien Moon itself — an unknown intelligence was waiting for the critical moment.”
Near fine; minor light corner crease.