My favorite book is up to 600 so I guess it no longer qualifies.

But for a hidden gem with fewer reviews, I will say "Because of You" by Lisa Walker. It only has 17 ratings on goodreads and is no longer in print. It follows the story of a girl from childhood into her early 20s, as she deals with a dysfunctional family and dysfunctional relationships. There are some interesting thoughts and observations that she offers along the way. I read it as a teenager when it came out, and I'd still consider it one of my all time favorites.