Is it identical to the books?
No. But nothing ever is. This was a well-done adaptation. As a fanfiction writer I see the merits and therefore didn't dismiss the series in the first episode. I'm glad I didn't give up on it. While there was a lot that was changed, much was the same and some of what was changed was necessary to flow and timeline.
Are there new characters, or characters that have been altered?
Yes.
Is the spirit of the story still there?
Mostly... the aging-up thing is a great trope in all fanfiction, but it stole the one thing I loved most... the coming-of-age part of the story.
Season one: Rewatchability... very high.
Season 2 rewatchability: TBD.