Take my opinion with a slight grain of salt because it's been at least a decade since I read the book and a half of the series that I got through, but from what I recall the books just didn't really have much to them - flat characters, awkward dialogue, and the actual prose itself was pretty bad. It was also boring enough that I just didn't care about anything that was happening, and I'd read enough good fantasy by the time I read Eragon that its flaws were hard to look past - I know the dude was a teenager when he wrote it, but that doesn't make the work magically better. Not trying to shit on anybody's parade, but it just really wasn't my thing.

I enjoyed the magic system at first, but it kept expanding and expanding to basically undo its own limitations. I remember being disappointed with the last book, but being especially disappointed by how it ended. It felt like a very forced attempt to have the same bittersweet ending Tolkien gave us in Lord of the Rings, but unlike in that, it felt completely unearned and illogical.

The books end that bad. The first couple were pretty good, but the ending was awful and ruined the whole series.