I am a voracious reader and my profession is essentially to read books, mostly fantasy and Sci-Fi, so I am but rarely surprised. This book is one of those surprises and most excellent one at that.
I found out about by watching a BookTube channel, Benjamin's Bookclub, and I credit this guy for discovering to me previously completely unknown writer.
Now, I'm a great fan of military science fiction, from Joe Haldeman through Lois McMaster Bujold and David Weber to new writers in the field, but this blend of high-stakes military action and horror of both psychological and body/gross kind was completely new to me. Something similar was done by Christopher Ruoccio in one of his Sun Eater books, but on much smaller scale, so The Crypt: Shakedown stands firmly in a niche of its own. If I had to force it into a box of some kind, I'd probably say that it reminds me the most of more realistic and non-satiric Warhammer 40k. This book is by definition grimdark. Its setting is randomly murderous in such a way that even GRRM would envy it, character don't even try to have any redeeming qualities in a totally Abercrombian manner, except with total lack of any humor whatsoever and their characterizations are done in broad but firm and precise strokes that I would compare to Dostoevsky if that wouldn't be sacrilegious and slightly ludicrous.
For the better part of the book nothing special happens (if you discount random acts of horror that permeate this novel); when the action comes, its hectic and confusing in a totally realistic way. In fact, this was one of more realistic descriptions of military life and combat that I have ever read (excluding the obvious, of course).
I really don't have enough words to recommend this one. I need to read more of Sigler's word in order to get a sense of him as an author, but The Crypt: Shakedown was so outstanding that I went to by the second novel in the series the moment I finished this one. Alas, there's no such thing as of yet.
Anyway, 5* for this one and Nightflier's Seal of Recommendation.