If one takes the original novellas of Bujold’s Vorkosigan Saga (collected in the volume Cordelia’s Honor), the The Warrior’s Apprentice is the second book of the series. In the first, four novellas in all, Betan Colonel Cordelia Naismith ends up stranded on an uninhabited planet with enemy Barrayan general Aras Vorkosigan. The two work together to get off-world. As the Barrayans rescue them, Cordelia is taken prisoner, but released back to Beta at Vorkosigan’s behest. The two have fallen in love, but the Betans think Cordelia has simply been brainwashed. She leaves Beta for Barrayar and eventually marries Vorkosigan, who becomes the Emperor’s regent. During a failed coup against the regency, the Vorkosigans are gassed with a poison which causes severe problems for their unborn child, Miles. The coup is put down, and Miles is spared with Vorkosigan maintaining a regency for the infant Emperor Gregor. Caught up?
Good. The Warrior’s Apprentice shifts the focus on Miles. His father, no longer regent as Gregor is a young man now, sends Miles to military school. Unfortunately, with the brittle bones resulting from his mother’s poisoning before he came to term, he manages to break both his legs and fail the physical part of his qualifying exams. Dejected, he goes to Beta to visit family with his bodyguard, Bothari, and Bothari’s daughter, Elena. There, Miles, on a whim, cons a freighter owner out of his obsolete freighter in order to keep the pilot employed, then takes a job with the freighter running arms to a distant (and primitive) planet wracked by civil war. They run afoul of the blockade, and Miles cons his way out by tricking the mercenaries into surrender to the fictitious Dendarii Mercenaries. By the time Miles cousin Ivan comes looking for him by order Aras Vorkosigan’s rival, he has welded the once-enemy and allied mercenary groups into an all-too-real Dendarii Mercenaries, turned a profit, and ended a civil war, mainly out of skill and luck. Meanwhile, back home, Vorkosigan’s rivals try to use Miles’s absence as a way to subvert the council of counts and the Emperor himself. Unfortunately for them, they are confonted with a wiser, more experienced, and very much alive Miles.
Bujold changes the tone of the series by focusing on Miles and Elena, childhood friends kept from being more by Barrayar’s class rules. In the beginning, it’s a fun romp, with Miles playing the part of a young Han Solo conning his way through everything. Indeed, while everything that goes Miles’s way comes through sheer luck, subterfuge, and projected confidence, Bujold leaves the reader well aware that this can all go horribly off the rails at any second. And even if he does manage to pull off his arms run or creating a brand new mercenary force out from scratch, back home, there are still some barbaric punishments awaiting him if someone chooses to make the case that he’s out to overthrow the Emperor (and never mind that Gregor was one of Miles’s childhood friends.) Miles grows to a sharp, observant young man in a short time while demonstrating an almost comic ability to BS his way out of almost any situation. In some ways, it’s a better backstory for Captain James T. Kirk than the one JJ Abrams gave us.