Recommend a Science Fiction Book - Any Genera

A couple of military SF books that are worth a look are the Subterrene Warseries:

and Embedded by Dan Abnett:

Anything by Cordwainer Smith (pseudonym of Paul Linebarger).

+1000 on A Canticle for Liebowitz, Walter M. Miller, Jr. Hilariously funny and heartbreakingly sad, often simultaneously.

I agree with both of these, though I’d have to say Cordwainer Smith is more of an acquired taste. His work is simply unlike anything else I’ve ever read, though I mean that in a good way. My favorite short story of his is The Game of Rat and Dragon.