I highly recommend "City Fights: Selected Histories of Urban Combat from World War Two to Vietnam." - Edited by Col. John Antal & Maj. Bradley Gericke.
"Death Ground: Today's American Infantry in Battle" - Daniel P. Bolger, is also good. I actually found it to be extremely informative.
On a different related side, "Shake Hands with the Devil," - Romeo Dallaire, also good.
"Plausible-Science-Fiction," wise, there's "The Last World War," - Dayton Ward. Which is an excellent piece of Sci-Fi. It's not "Here's a phaser, go shoot the Klingon," it's more; "The little grey alien dudes are... about seven foot, hard to kill, and you've got an M-16A2 that's only really effective against them inside of eighty meters. By the way, they've got little energy-pulse weapons that'll tear you apart."
Good stuff, all of them. I've got more, but that's all for now. And then there's "War of the Rats" / "Rattenkrieg," - David L. Robbins; which is mentioned on the site.
"My Jihad" is less than plausible but not quite what you think it is. Aukai Collins wrote that one.
One legged because he caught a burst from an RPK while enroute to a village with the rest of his Mujahideen friends, who decided to gaggle up and very nearly let the entire OMON force annhilate them. (If it were proper Spetsnaz, they'd all be dead. There'd be no book then.)
And yeah, you nailed it. It's an interesting read, especially when Abu (Their nickname for Collins) becomes "Big Man" later, around the KLA compounds and whatnot. Attempting to organize your way into Chechnya... that's the part I didn't find plausible in the slightest.
Although the rounddance the CIA goes through, that's plausible.
Plenty of stories about LRRP, LRP, MACV-SOG, and suchlike in any one of James R. Linderer (I believe....) books, in particular the "Phantom Warriors" series. Then there's "Rangers in Vietnam," and several dozen on SEALs. Then there's "Stingray," about Marine Force Recon in 'Nam as well.
I'm surprised no-one has mentioned 13 Cent Killers, do not know the author's name, and then there's one of my personal favourites, "Chickenhawk." The title alone should be enough, because I unfortunately forget the author's name.
SAS Secret war. It is about the SAS in the middle east fighting an insurgency in the 60'-70' It is the best book on counterinsurgency I have read and is required reading at the British war collage. It is out of print now, but can be found on line used. It also goes by another name called operation--------. I cant remember now.