Continuing from last time, my next group are books that are series, which again I've re-read on a regular basis, and are listed in no particular order of preference:
The Heritage Trilogy by Ian Douglas.
Tales of the Starwolf by David Gerrold.
The Honor Harrington series by David Webber (first three).
The Confederation series by Tanya Huff.
I have lost count of how many times I've read and re-read The Heritage Trilogy by Ian Douglas, a pseudonym of William H. Keith Jr., who I first came across when I read a BattleTech book called Decision at Thunder Rift.
Some parts of The Heritage Trilogy is now rather dated, as in we are in the time where certain events have happened that didn't, which when reading the first trilogy you have to sweep past. I should also mention that the trilogy has two sequel trilogies and I'm equally besotted with them despite some hoary old clichés.
In short, it's Marines in Space and I love it because it captures the Marine esprit de corps.
Tales of the Star Wolf roots can be seen in Gerrold's Yesterday's Children, which was later revised as Starhunt. The former is basically a Star Trek story with the serial numbers filed off: evident in original ending of Yesterday's Children where the captain is proved right, whereas in Starhunt Gerrold's protagonist suspicions of the existence of an enemy ship shadowing them is proven right.
Then Starhunt was expanded by the addition of a sequel series called Tales of the Star Wolf a three volume compilation of: Voyage of the Starwolf, Middle of Nowhere, and Blood & Fire (which is much easier to get hold of as an omnibus than the trade paperback individual editions). What's interesting about this series is the way Gerrold revised and refined the core story through several iterations.
On Basilisk Station is the first book in David Webber's Honor Harrington series, and in many ways it's the best because it's a lean mean, tightly written novel.
As a series it only loses its way around the end of book five, which I know will offend some fans, but as Webber said in a Baen podcast his original intention was to have Honor die in book seven. Choosing not to kill her has actually caused problems with the over arching story arc that was originally planned. Well, if only I had his problems with my series. Colour me envious.
Finally, for this tranche of books, Tanya Huff's Confederation series that starts with Valor's Choice, which is a blatant retelling of Rorke's Drift.
Despite that, the book is engaging because the main character is likeable, and the sequels move the plot forward in an interesting manner with the reveal of the Others: plastic aliens want to be your special pal.
The sixth book, An Ancient Peace, is no longer purely military science fiction because the main character has left the Confederation Marines and is working as a private contractor for the Confederation: I would class it as mildly military, a not uncommon trait of military SF series. By that I mean the characters act as civilians rather than soldiers who follow a chain-of-command.
NB: I'm surprising myself with how much I want to write and so there will be several more parts to this series as I work through my military SF collection.