I didn't care for the ep.
I do think Kes had a lot of unexplored potential; it's a shame so little was done with her.
As for books, they're a nice source of potential explanations and cool ideas, at the very least. However, as books are non-canon, I'm quite disappointed at how seldom alternate universes are explored. Indeed, Trek is better at doing this than many continuations of former TV series. And the most obvious change is to bring back former characters - there can be no excuses as to actor unavailability, or lack of budget, etc.