The Starfist series isn't too bad for a kick back, knuckle-dragging military sci-fi romp. The plots are far from deep (we're usually talking kiddie pool here), but serve as sufficient vessels to push the action along. Read these moreso for the action and Semper Fi, kill em all mentality rather than an introspective on xenos discovery and it's impact on the human race.
I particuarly enjoyed Anathem, especailly since it hit on many different subjects simultaneously -- ranging from religion, to mathematics, to politics -- while still having an interesting story. Not an easy read, what with the heavily customized vocabulary and all, but worth it in my opinion. It's not much in the way of military sci-fi until fairly late in the book, but still a good read.
I'd stay away from David Webber's Off Armageddon Reef (Safehold) series, or any of his newer works for that matter. Though I'm only reading the first book now, it's a bad diversion from his sole-authored and collaborative works in terms of writing style. Characters often go into deep, internal monologues for sometimes tens of pages at a time which do nothing to further the plot. A scene which has perhaps five paragraphs worth of actual plot progression is laced with pages of supplimental information on politics and nations that reads like a text book, all of which could easily be integrated as the story progressed.
Others seem to agree -- the universes, stories, and settings Webber creates may draw from many existing or historical sources, but are still very good in their underlying merit. It's just that as his works grow in popularity -- and consequently length -- there's a lot of residual political or superficial near-filler material that does nothing for the book as a whole. As one reviewer put it: "Robert Jordan syndrome." The Wheel of Time books suffered the same fate.
Most of the Warhammer 40k stuff is OK, especially if you start getting away from the Space Marine books. I've found the Soul Drinkers series the best when it comes non-Hours Heracy Space Marine books. The Eisenhorn series was good, though gets a bit slow from time to time. There was also one book I read years ago that dealt with an Arbites member, though I'll be damned if I can remember what it was.
The Lost Fleet series was okay. Not bad, but it's to Honor Harrington as Starfist is to the Forever War: some action and drama, but not too robust on the plot or subtle meanings. Basically, an easy space-opera read. That being said, I read it years ago and perhaps my memory is a bit foggy.
The Mote in Gods Eye was pretty good, but I haven't read any in the series past that. It's an interesting first-response read, though the alien's really make the book. The characters, are pretty flat and don't really develop. Seeing as how the alien's feel more the central point of the story and not the humans, I don't really see that as much of a downside.
I'll also toss in Forge of God, though that's probably not what you're looking for until the second book, Anvil of Stars. It's very heavy on politics and drama surrounding the end of the world after aliens decide they want to eat the planet, but doesn't get "military" like till the second book. Even then it might be a stretch, and you have to read the very non-military Forge of God to get to Anvil of Stars.
Richard K Morgan's The Takeshi Kovacs series.
Seconded. The plot and moral opportunities and consequences presented and explored by Morgan when someone can't really die and can change bodies at will is phenomenal. Plus, the series is written with a bit of a 50's detective noir style, which goes very well with most of the plot. For some reason, some of the writing style reminded me of Max Payne
😛
I'll also second Old Man's War and Forever War. Old Man's War is akin to Starfist, being an easy read that keeps the action going with new locations and people, yet doesn't slow itself down with an overly complex plot. Forever War is mostly the opposite: it deals with a lot of cultural and psychological issues when decades or centuries can pass from one campaign to the next. There's some residual politics left over due to the author's military background and when it was written, but that kinda complements the plot if I do say so.
(Hrm...looks like I pulled a Robert Jordan myself and got too long winded...oops)