Lucky Starr and the Big Sun of Mercury by Paul French (Isaac Asimov)
Hardcover: Doubleday, $2.50, 191pp, 1956
Project Light involves investigation into the nature of light in hyperspace which may have implications for energy and weather control on Earth but someone or something is sabotaging the project. Lucky Starr and John Bigman Jones are on Mercury to investigate and have to deal with several people who may be friend or foe, including a project manager who is stressed to the point of insanity, a base leader who sees menacing Sirians under his bed, and a lieutenant of a Senator bent on exposing “waste” and destroying Lucky’s employers, the Council of Science. Over the course of events, Starr and Jones will face death separately and solve the mystery together.
There are several problems with this book ranging from minor to middling which cumulatively become major. The opening behavior from the project engineer is too extreme and the lack of consequences for it is mystifying. The stress constantly laid upon Lucky’s anonymity while having everyone in the Solar System identify him is pointless and annoying. While villains are not meant to be lovable, the unmitigated repugnance of the Senator’s lackey is difficult to bear. The isolated nature of something in the old mine shafts which should be part of a system is a problem. More seriously, Lucky is made to be pretty stupid once and, though Bigman is the sidekick and still has his clever and heroic moments, he is made to be extremely stupid at least twice, if not three times.
While not exactly a problem, it’s at least odd that, with Asimov having dispensed with the unneeded “French” persona , he goes the opposite way and declares that all worlds in the Galaxy are settled with quadrillions of people (despite this having been and still being essentially confined to the Solar System). Further, the Sirians are now directly described, without using the word, as Spacers and (no spoiler, because it’s on more than one cover), positronic robots are introduced with the Three Laws paraphrased. In fact, there are specific echoes of “Runaround,” in which Donovan and Powell went to Mercury to see about restarting a mining operation. But only the robot really has anything to do with the plot and it’s not really necessary for it to be a positronic three-law robot.
All that said, this is an efficiently constructed tale at its core and, like the Venus adventure, has a good setting  that’s put to good use in Chapter 10, where readers, via Lucky and his somewhat magical inso-suit, are transported from wherever they happen to be reading to the surface of Mercury in order to experience its “big sun” in one of those exhilarating moments which are a big part of what makes science fiction so much fun.
 As usual, Asimov includes a Foreword to warn the reader that, though it was published in 1956 with the best intention of being accurate, subsequent exploration has determined that Mercury does rotate rather than having one side always facing the sun. (However, unlike some stories which make tidal locking a central element with many ramifications extending from that, it’s not an overwhelming issue in this one.)