Beyond Apollo (original 1972; edition 1974)

Malzberg has always combined a passion for science fiction and an encyclopedic knowledge of its literature with a moody temperment that looked for the dark side of SF's traditional sunny optimism. ...The task of deciphering Harry Evan's diary of what happened to him, and the rest of the crew, on that fateful expedition to Venus may be as difficult for the readers of Beyond Apollo as it is for the people who sent him on that journey, or for Evans himself. -- Masterpieces of Science Fiction