Jan Valtin was pseudonym of Richard Julius Herman Krebs,  author of the wildly popular "OUT OF THE NIGHT." Now out-of-print, this was a seven hundred fifty page book which sold a million copies in 1941 and was a Book-of-the Month Club selection. 

The autobiography of a renegade German communist agent, Jan Valtin/Richard Krebs, the book described his intrigues throughout the world and capture and torture by the Gestapo. Having convinced them he changed political allegiance, he was permitted to leave Germany as THEIR agent, his wife and son remaining as hostages.

Failing to gain Communist support for their rescue and afoul of bureaucratic politics, he narrowly avoided kidnap to Russia and execution. After flight to America he wrote the book,  served 39 months in San Quentin, testified before Congress' Un-American Activities Committee, was pardoned by the Governor of California for a (deliberately) botched assault committed years before, drafted into the Army, re-married and had another family.

He died in 1951 of pneumonia, screaming nightmares of torture on his deathbed, by then being (of all things) a PTA member in Maryland.  The  book is available used and, still, well worth reading.