A pretty compelling read, especially given the fact that it takes place but one year after the battle of Yavin. It features a character we've read about in the Thrawn atrilogy. Unsurprisingly, given the fact that it's written by Timothy Zahn.

No doubt about it, this really has the OT feeling to it, but in book form this time. You also get Han, Luke, Leia, and of course Chewie. The title, being as it is, "allegiance" could be explained pretty easily, and I can summarize it thus, and with a single word. Stormtroopers!

A bunch of stormtroopers learn about the way the empire really is and decide to desert. Well, I'll let you see what happens. Do they join the rebelion? Will they be executed? RAFO.
You also get a few conspiracies, involving some local gangs of space pirates. And frankly, I quite enjoyed the scenes where the pirate conspiracy got untanggled. This is, after all, half of the book.
I've appreciated the fact that, we got to see that stormtroopers are not the evil white bucketheads, which follow orders without questions or complaints, no matter how cruel or unjust those orders are. In fact, there are some stormtroopers who think and believe, or rather believed in what the empire was supposed to be, " Freedom, justice and security." As the saying goes.

The rest will be for you to find out.