If you mean the sequels, prequels, interquels made by Brian Herbert and Kevin J Anderson, then those are of a lower quality. They had the good fortune to inherit an IP and just ran with it. They may not be so bad as far as the genre goes (except for Sandworms), but they create a somewhat wider context. It's not for everyone, while I feel the originals of Frank Herbert may be, at least to people with a taste for sci-fi.
The prequels shouldn't have been written.
I'll admit to not having gotten that far; two bad sequels was enough for me to give up.
My English is a bit better now, and I like to think I've become a bit more patient ;) So perhaps I could attempt it again and see if I appreciate it more.
Incidentally I agree, while the first two sequels are interesting they are a bit of a slow read and they don't feel as well written as the later books. Frank Herbert really starts to get into his stride with the Emperor God of Dune.
The books by Brian Herbert and Kevin J Anderson are better avoided like all works by Kevin J Anderson (who is IMO a very mediocre writer)
I quite enjoyed the Jedi Academy trilogy, both for its own sake and for its detail on several bits of the universe.
A lot of people think Dune is a straightforward hero story, with Paul Atreides the "good" hero, but actually (edit: I should say, according to Herbert and taking into account the later novels) it is the story of the terrible damage a "hero" can cause to a culture and society.
"No more terrible disaster could befall your people than for them to fall into the hands of a Hero." - Frank Herbert
This is similar to Cryptonomicom, which people think is the story of Avi and Randy's success, but is really the story of their misguided quest which is doomed to fail.
But my enduring memory was of a flawed young man becoming overly enamoured with his new messianic role, and making some choices that were questionable.
However, while the first novel was the most digestible and most intriguing plot-wise, it is the sequels that explore the philosophical, political and social subjects of the original much more deeply. In a way the sequels are sometimes more like (huge) essays on various philosophical topics that merely use the original story as a backdrop.
The start of the book is maybe a bit slow but it does pick up pace rapidly after a point. The best advice I got was to just push on, I'll understand why later. I don't regret it.
It's depth barely scratches what comes next, especially in the 4-5-6 books. Even though there are inconsistencies the last 3 books are much much better in my opinion, especially the fourth.
The first book is just an (almost boring) introduction.
The first two books are meant to be read as one. I recommend, at minimum, Dune and Dune Messiah.
Obligatory XKCD link - https://xkcd.com/304/
Enders game is a space battle thriller with a great twist.
Speaker is all about what do you consider "human" and what do you consider "alien". It was very mind expanding when I was 14.
However, it's also the kind of book that should never have had a sequel; other books in the series not only don't measure up, but actively undermine what made the original interesting. It's possible that other good stories could have been written in that universe, but they weren't. I highly recommend reading only the original.