This book 5 in the Dragonback series, and none of it will make much sense if you haven't read at least the first one, Dragon and Thief. And further, as the action gets hotter and starts to point to a conclusion of the series, the cliffhanger aspect is pretty bad. I think it would be wise to say that not only should you not start with this volume, you should wait to read the series until it's all out. (Unfortunately, the way the publishing industry works, you have to buy book now anyway, or you may not be able to when the last one is there. Stupid publishing industry.)
The story is certainly getting more morally complex, and we're getting some character development, as well as some interesting development in the human/K'Da relationship. Jack and the reader learn a fair bit about his back story. There's some major shifting in the direction of the series story arc; hopefully I'm not saying too much to say that the overall quest, which seemed hopeless before this book, now looks merely difficult and dangerous. As hard to swallow as the concept of the K'Da is, my inner 4 year old really wants one for a friend, so the thought that Jack and Draycos can save the race is a happy one. There's a lot of action, and less deus ex machina stuff than some. With all that positive stuff, it's certainly a stronger book than some of the previous volumes, but it's still not entirely satisfying; I think partly because Zahn works so hard to create a sense of breathless urgency that he leaves the reader a bit confused.
I think that boils down to an 8 out of 10.
**** PLOT SUMMARY -- MASSIVE SPOILERS ****
At the beginning of the story, Alison, Taneem, Jack, Draycos, and Uncle Virge are all together. Jack almost succeeds in hacking into the Malison Ring's (the mercenary outfit that provided the ships that wiped out the rest of Draycos' advance party) computer. But he doesn't, so they head to the next Malison base. Except that Jack decides that they'll go to the second closest one, and stop along the way at Semaline, a planet where Uncle Virgil maintained a safety deposit box. Jack heads off, by himself, and promptly gets nabbed by a couple of the native Golvins, who insist he is the "JuPa" and drag him off to their primitive settlement, having surreptitiously relieved him of his comm clip and his tangler. Jack finds himself in a weird position; the natives set him up as some kind of a judge. They seem to almost revere him, but the head Golvin ("the One among many") clearly wants to stay in control. Supposedly his parents died at a mine here, but the One doesn't want to let him investigate. When he does anyway, he finds suspicious things. Somewhere along the line, he figures out that "JuPa" is the native's expression of "Judge-Paladin". Judge-Paladins are a slightly mysterious frontier justice force. And his parents were the ones who visited the benighted Golvins before and got them set up. They tried to mediate a dispute over the ownership of the mine, and got killed doing it. The ultimate reason for the dispute was apparently an attempt to manipulate the price of the mining company, so that Braxton could buy it cheaper, which leaves Jack thinking that Cornelius Braxton may have been responsible for his parent's death, though the others all think it was probably Arthur Neverlin (who was Braxton's second in command before he betrayed his boss in an earlier book). Along the way to learning this, Jack discovers a StarForce pilot who's been held prisoner for five years after he accidentally killed some Golvins when they were where they shouldn't have been and he landed his Djinn-90 on them. Jack learns most of the details from the fixer who killed his parents, who comes back in response to the report that another JuPa had arrived. The fixer tries to kill him, but with the help of Draycos, he survives the explosion, activates a piece of mining equipment, and gets out. Then he fights the fixer hand to hand, and just as he's being strangled, Draycos kills the fixer. They form a plan to rescue the pilot, steal the fixer's ship, and split, but unfortunately, Draycos takes a crossbow bolt. They hide in one of the towers while Draycos recovers partially, and then try to escape again. They appear to have been caught, but the pilot sacrifices himself. Jack wants to try to rescue him, but Draycos makes him leave. They're trying to head for the pilot's wrecked fighter, but conveniently run into the Essenay, which gets them out of there. Jack doesn't know the pilot lived, but when the real Malison Ring force shows up shortly, he ends up with them, and the last we see of him he seems to be talking them into believing he wants to join them so he can get to Jack and kill him for leaving him behind.
As to how the Essenay finally showed up for the rescue: When Jack turns up missing, Alison and Taneem go to look for him, but they can't turn up anything past the point where they lost his signal. Alison decides to go to the bank and clean out the safe deposit box for him. She doesn't have the key, but she's a clever enough thief not to need it. She's not good enough, though, to not get taken by the thugs who've been waiting for years for someone to clean out that box. But she manages to talk them into believing that she never heard of Jack Morgan; she just specializes in cleaning out abandoned safety deposit boxes. She convinces the thugs she's an expert safe cracker, and soon finds herself on Arthur Neverlin's ship, which takes her back to the Chookoock estate on Brum-a-Dum where the enslavement in Dragon and Slave occurred. Combining her safecracking skills (which are good but not that good) with Taneem's dimensional superpowers, she manages to figure out the safe. There's a regular lock, but there's also a self-destruct mechanism, which is defeated by putting K'Da claws into the right two of 20 indentations along the door. Unfortunately, figuring this out means that Neverlin has the contents of the safe, and probably now knows the rendezvous point the K'Da fleet is coming to. And to make things worse, rather than paying her, her employers tell a flunky to take her out back and shoot her. The flunky, of course, wasn't expecting Taneem, and they manage to hide and foment a slave revolt, which is almost working when the real Malison Ring force that Alison had earlier called in using the access codes she'd stolen in the last book shows up. The real Malison Ring folks aren't likely to be too happy with the arrangements Colonel Frost made, but it's still far from clear that they won't still let Neverlin work out his plan. But Alison manages to brass-balls her way into letting her walk out with the slaves, where she meets up with Uncle Virge, who first tracked her to Brum-a-Dum, then returned to Semaline for Jack, and then came to Brum-a-Dum again. At the end of the book, Alison presents some clever thinking to narrow down to a single system where the bad guys have to have headed to collect their extra-galactic Death Weapon to wipe out the fleet with.
In the next book, look for the pilot causing chaos on the inside while the two human-K'Da teams take out Neverlin and his plot, or at least move a book closer to it.