DFR benefits from having the groundwork laid by Heir to the Empire quite a bit - every existing player in the book except 2 (Garm Bel Iblis and Niles Ferrier) are from the prior book, while most of the plot of this book is directly set up by the prior book's cliffhangers as well. The plot of this book features the following storylines:
1. Leia goes off to the homeworld of the Noghri, where she tries to make amends for the destruction of their world and to convince them the Empire is simply using them;
2. Luke heads off to Jomark to meet Joruus C'baoth, where he tries to see if this is a Jedi Master he can learn from, and if not, if he's someone Luke can help.
3. Mara Jade begins to feel the force return to her and at the same time tries to help Karrde evade Thrawn's grasp, eventually leading to her needing Luke's help to rescue Karrde from Thrawn.
4. Han and Lando go out to try and find incriminating evidence against Bothan Borsk Fey'yla and to exculpate Admiral Ackbar from the treason charges against him and wind up discovering a forgotten former Rebel General/Senator
5. The last two plots combine to form the finale, where the main characters attempt to race to a fleet of lost warships which might turn the tide in the battle between the Empire and New Republic.
You'll note that one of those plots, #3, basically has no involvement of our major movie characters whatsoever until the very end (when Luke and Mara team up). That's the benefit of Heir's setup here - we're interested in both Mara and Karrde's fate from the start, without the need for major characters crossing their paths. Incidentally, this book would be more logically called "The Force Awakens" for this plotline with Mara than the movie is (more on that tomorrow).
Most of the rest of these plotlines work as well. The Noghri plot works really well and is very impactful and Luke's reaction to C'baoth is very believable and really works up how the mad jedi is trying to "train" Luke in a different way than we'd previously seen Vader/Emperor work on turning him to the Dark Side.
Han and Lando's plotline is a bit more hit or miss. Garm Bel Iblis would become more of a major character as a master tactician in the Expanded Universe, but here he comes off as whiny - it doesn't help that Mon Mothma's influence really isn't shown that heavily in the movies (one scene in ROTJ!) or Heir. (This problem will extend to The Last Command as well). The sequence of events that leads them to him is well...very coincidental even for a series such as this,
And then there's Niles Ferrier, the other major character introduced in this book. He's just a bad character (along with his Wraith who isn't even named) altogether and basically just a plot device. So he's a master ship thief but who smokes a distinctive type of Cigar such that Lando and Luke (and presumably others) can identify him basically anywhere by smell? Really? Speaking of coincidences, him showing up magically on the next planet Luke and Lando go to a few chapters after meeting them in the opener is something. Again, he's basically a plot device who leads the characters from point A to point B and this is probably why he'd never be seen in the EU again after The Last Command (yes he dies in that book, but he never appears in books set prior to this trilogy either).
The other real flaw in the book is the Fey'lya plot is...well, kind of lousy. A regular flaw of the expanded universe in Star Wars is that non-human races frequently get treated as a group of individuals all of whom share the same traits - in this case, Bothans are treated as sneaky power grubbing aliens. Fey'lya is the ur-example of that (and alas, he's not alone) and it doesn't help that he's just so comically ineffective at doing anything. The "speaking into an unexpectedly live mic" strategy that dooms him in the end is cheesy and well, the treason charges of Admiral Ackbar are actually never cleared in this book - it's cleared offpage in between this book and The Last Command (by Talon Karrde's slicer, Ghent).
Again, these are basically nitpicks. Most of this book works really well and the finale of the book is definitely earned. And like Empire, this book functions as a table setter for the trilogy's finale, as the good guys get their butts handed to them and learn the true nature of Thrawn's plan - the Clones. And the book also sets up Thrawn's fallibility - numerous times he makes the wrong determination from the evidence at hand - due to making false assumptions as part of his thinking process. And with the Noghri starting to turn against Thrawn, the seeds for the good guys' final triumph are set.
That said, this would again be really tricky to film. As I detail above, there are four separate plots going on simultaneously for most of the book, wit the characters all separate in different locations. In the original trilogy, the split is at most 3-way (ROTJ where Lando is in space, Han & Leia on the planet, Luke on the Death Star), and even there, those plots are related and in the same area. This split is more like something you'd see on a TV Show, bouncing around between separate plots before everything culminates in the finale.
On that finale Heir and DFR end with all of their plots converging into a single plotwith seemingly large stakes at risk (of course, Thrawn has basically already won the large stakes before the finale of DFR). This is of course similar to Eps 4 and 5, which also have all plots converge at the end. Return of the Jedi does not have all the characters converge in one area at the end, and as we'll see tomorrow, neither does the finale: The Last Command.