If you like mil-fic/sci-fi, you might like Jerry Pournelle's "King David's Spaceship"; "March To The Sea" is like that in many ways.
http://www.baenebooks.com/p-575-king...spaceship.aspx
Baen has several Pournelle omnibuses:
CoDominium Future History Bundle (9 books for $36.00):
http://www.baenebooks.com/p-574-codo...ry-bundle.aspx
http://www.baenebooks.com/p-322-the-prince.aspx
4 books - a sweet deal for $5.00
"Publisher's Note: The Prince was previously published in four parts as Falkenberg's Legion and Prince of Mercenaries by Jerry Pournelle, and Go Tell the Spartans and Prince of Sparta by Jerry Pournelle and S.M. Stirling. This is the first complete edition."
Some of Stirling's best books are not published by Baen - the "Island In The Sea Of Time" series (published by Roc), "The Peshawar Lancers" and "Shikari In Galveston" (in "Worlds That Weren't")
Also, have you looked at the Lord Kalvan books. I haven't seen the original H.Beam Piper novel in ebook, but the Roland Green and John F. Carr successors are available at amazon.