There was, I’m afraid, a definite decline in the series. The first book did not reinvent the wheel but was, nonetheless, a reasonably creative take on the high fantasy tropes. The hero was a youth, but he never did turn out to be some destined hero of prophecy (or great wizard or even better than a decent warrior). The first book also took its time. Really took its time. Which was just fine.
As the series went on, the author started doing the George R.R. Martin multiple perspective thing and it didn’t work for me.
Also, the ending feels rushed and sort of implies that everything every character ever did was kind of pointless. And I’m also not entirely sure how the good guys won.