There's a lot of interesting stuff there, ethics of war, cloning, fighting, etc.
Usually, it's compared to Heinlein's Starship Troopers but that's a simplistic view. Occasionally, Joe Haldeman's Forever War is invoked, but that's a bit of a stretch.
If you liked this book, please read:
- Cyteen, by C.J. Cherryh -- a long-term war, colonies against each other, and one side using cloned troops. OMW's cloning is different, and similar, and gives a nice alternate view. Cyteen is a core book in Cherry's Merchanter/Alliance universe, including great books such as Merchanter's Luck, 40,000 in Gehenna, and many more.
- The Retief books by Keith Laumer and the Uplift books by David Brin. Only in that they deal with lots of strange aliens who don't think like we do.
- On that note, Ender's Game and Speaker for the Dead by Orson Scott Card, for how we deal with aliens that we can not comprehend, what OSC calls the varelse.
- Childhood's End by Arthur C. Clarke. I'm not a big fan of Clarke's writing, which is long on travelogue, and short on plot, but this does a great job of showing us that our minds are not recognizable to our parents, and our children's are not recognizable to us. There's some great moments in OMW between John and Jane that made me think of this.
Scalzi's relatively new to fiction... let's hope he keeps up this level of quality.