Dark Force Rising is an excellent follow up to Heir to the Empire (henceforth known as Volume I). Timothy Zahn has clearly outdone his previous novel.
Part two of the Thrawn Trilogy starts off immediately where the previous volume leaves off. After smuggler chief Talon Karrde's base on the planet of Myrrk was overran by Imperials, his organization is now forced to regroup. Among them is Mara Jade, who soon separates and starts her own journey of self-exploration. Despite her extreme hate for Luke Skywalker, in Dark Force Rising she will call upon his help. Along the way she will make some very important self-discoveries that drastically impact all Star Wars novels thereafter. Grand Admiral Thrawn, meanwhile has a few tricks up his sleeve as he battles the New Republic. Not only is he tormenting the Republic on a military level but he also has an inside leak that is called "Delta Source" that is becoming an extreme nuisance to the Republic. Meanwhile, Borsk Fey'lya--who was introduced in Volume I--has stepped up his power plays within the New Republic and is targeting them at Admiral Ackbar's expense. All the while, Pregnant Leia tries to balance the weight of the political office before she becomes engrossed on a dangerous quest of her own. All before the twins are born--which will happen here. Han and Lando are in a race to find the Katana Fleet, also called the Dark Force. Hence the name of the novel (in a well orchestrated pun). However, Thrawn is one step ahead. In the end, all of these many intriguing plots climax in an explosive conclusion....
Dark Force Rising is my personal favorite of Timothy Zahn's Thrawn Trilogy. While not much better or worse than the other two volumes (they really should be considered one story), the ending was simply the most intriguing to me. The plot mentioned above regarding Fey'lya comes to a head in a very satisfying way.
Two more important characters are revealed in this story. First is the mysterious Garm Bel Iblis. Like many of Zahn's characters, he will play a vital role in many future stories--and gives us an important insight to the past. Also introduced is the pesky but entertaining Niles Ferrier. While not making a lasting impact like Bel Iblis, he is a very entertaining aspect of this trilogy until the end.
As with Volume I, Zahn weaves together a very fascinating experience in the Star Wars universe. As we come to expect, it is very heavy with the political aspects. Of course, there is a strong plot featuring Luke continuing his training in the force with the becoming-ever-insane Joruus C'Boath. In this story, the separation between antagonists Thrawn and C'Boath becomes even more evident.
The references to the original trilogy slightly become less prevalent here (unlike in Volume I where they become slightly cumbersome). However, there are some similar parallels such as when Luke and Mara seek to break Talon Karrde out of a Star Destroyer. This is very similar to the storyline of breaking Lea out of the Death Star in Episode Four.
Lastly, it is worth mentioning, that the underlying feeling one gets in reading Dark Force Rising is that it feels and reads like one is living in the George Lucas created universe. While all three volumes of this excellent trilogy are recommended, this one is slightly above the others based on the very entertaining ending. Admittedly, the story moves around very quickly and from planet to planet in the first few chapters; but it is not a hindrance in any way. After Volume I is finished, you need (and should) pick up Dark Force Rising immediately!