Even moreso than Shattered Empire, Chuck Wendig's Aftermath suffers under the weight of expectations. The novel counterpart to Shattered Empire's comic book series (in that it is the first novel, rather than comic book, of the new canon set after Return of the Jedi), it not only being billed as an important stepping stone towards the world of The Force Awakens, but the circumstances of its release automatically put it into comparison to Timothy Zahn's novel, Heir to the Empire. But not only was Heir the first post-Jedi novel of the old Expanded Universe (it certainly wasn't the first original fiction Star Wars novel, but it did kick off the modern resurgence in Star Wars that hasn't abated since and is generally considered to have begun what fans think of when they think "Expanded Universe), it also remains, to this day, the most acclaimed of Star Wars novels, routinely considered both the best of the lot and most fans' favorite.
Aftermath, then, is cursed twice over; before even a word was written, it was setup to both tell a new version of events post-Jedi and detail those events in a way comparable to everyone's favorite Star Wars book. Of course, it fails to live up to Heir, but that's not entirely its fault: nothing in this day and age could, and to Wendig's credit, he doesn't try to live up to it; the story he tells is an entirely different beast than Heir, at times both more and less concerned with the big picture of the galaxy than Heir was. And as much as this book invites circumstantial comparisons, it's also been released under vastly different circumstances: it's not ending a drought of new Star Wars stories, and it exists as but one narrative brick (albeit a large one) in a house that is being very carefully constructed, whereas Heir was written and released with relatively little oversight by LucasFilm, while most of the people reading Aftermath (especially the ones being overly-critical of it) are much older, with many more Star Wars stories under their belt, than when they first encountered Heir.