This is a series, as witness the theme naming -- all the books named after spaceships -- with an unusual degree of self-containedness in the novels. This is certainly not a novel divided into six volumes. However, there is an overarching story. I would recommend reading in order.
Dauntless opens with the main character, John Geary, making his way through the title Alliance ship, rather in a daze. He had been woken out stasis in a survival pod to find a century had passed, everyone whom he knew had died, and that the war was still going on, when he had landed in that pod during the first, surprise attack. And his efforts there had turned him into a legend -- with the tale that one day, Black Jack Geary would return to save them all . (A very awkward belief to have everyone around you believing.)
The admiral who was fleet commander passed command to him while he and other flag officers went to negiotiate with the enemy for surrender terms after a devasting battle. (Geary had missed most of it, being dazed.) And then they are all massacred, and the Syndic enemies order their immediate and unconditional surrender.
Being in actual, effective command does a great deal to break him out of his daze. He starts to organize, discovers some changes in the fleet since his day, which are not improvements in its fighting ability, and sets out to escape the system. And learns he has a great-nephew in the fleet who hates him from living under his shadow. And that's how he starts out on the mission of getting his fleet back to Alliance space. Despite political infighting, the necessity of constant out-witting the enemy, and severe lack of supplies.
All of which keeps him on his toes for six books, with some intriguing personal developments. The space battles' tactics are laid out in quite a bit of detail. There was one element that seemed rather incongruous when introduced, but proves to be quite intregal to the story.