Jay Allen’s Crimson Worlds series is a great, pulpy military sci fi series. The first is annoyingly in first person but the rest are in the normal third person. Power Armour, militias, space fighting, heroes, villains. They are some of my favourite sci fi novels, because they are so easy to read and I actually cared about the characters.
Late entry for a small series by the Grand Master of ‘Knocking out books in 5 minutes flat’ are the Damned series by Alan Dean Foster. In a sentence – Aliens are sh*t at War, and one side, which is getting its butt kicked in a vast interstellar conflict, goes out looking for intelligent species to help it out, and stumbles across Earth. By coincidence the Human they select as their agent is a Arty Pacifist, who does not like what they have in mind.
Like all ADF they are trash, but trash with moments of treasure in them.
also, if you can find them, ‘the VC’s’ was an sweet little alien War in Space series from 2000AD, and there was a later series with similar ideas but a bit more ‘War is Hell’ called ‘Bad Company.’ Good, if you can cope with the slightly goofy artwork that I always found made it harder to enjoy than the earlier Boys Comic style illustration of older 2000AD stuff.
If you like Larry Niven, you might want to try the Man-Kzin Wars series. It’s not Niven, Niven franchised his war to whomever might want to try it out, and a great many authors have written their takes on various episodes. It’s not a novel nor a series of novels, but it’s multi-volume; some of the contributions are novella length, and there’s a unifying theme. I dug it: