A great SF author you've never heard of

Grant Callin wrote a handful of short stories -- four in total -- and wrote a novel that functioned as a sequel to one of them. He then expanded the short story into a novel. That's the entirety of his output. All I've read are his two novels. Saturnalia, the expansion of the short story "Saturn Alia", and the sequel A Lion on Tharthee, which I don't like as much, but it is still extremely good. Saturnalia is basically a treasure hunt in the Saturn system. It's glorious. It is, to my mind, very reminiscent of Heinlein's style of writing in how readable and flowing the narrative is. Yet despite its readability, it is definitely hard science-fiction: Callin knows his stuff, and what he doesn't know, he fakes very well. Take this passage from the beginning of Saturnalia:

"Listen Whitey," he came back. "I'm a SpaceHome maintenance specialist -- been one for twenty-five years. And if there's one thing I've learned, it's to expect the unexpected. We been livin' up here for over fifty years now, and we're still learnin' about the environment -- cosmic burst anomalies, vacuum-induced bearing creep, lubricant outgassing, trapped corona discharge, and on and on. Every time we think we've got a problem licked and begin to start congratulating ourselves, it shows up again in a different form, and -- bingo! -- we got a new long-term environmental phenomenon to worry about."

That sounds absolutely real to me, real conditions of living in space. Callin's focus on technology (and piloting spacecraft) may not be everyone's cup of tea, but I enjoy it, and engineers (and pilots) should absolutely love it. The only weakness to both books is that they have too much bonhomme camaraderie. You know what I mean: the main characters are diamonds in the rough in some sense, and people are always able to see through the exterior and recognize how truly deep and noble they are. Heinlein does this too, but Callin's is so over the top that it gets distracting. Another minor weakness is that Lion on Tharthee begins with a clear statement of the myth of conflict between science and religion, but that's so common to science-fiction that you can't hold it against anyone (although more recent science-fiction writings seem to be correcting this misunderstanding). Regardless whatever weaknesses the books may have are very minor and are heavily outweighed by the positives. I strongly recommend these books to everyone who likes science-fiction.