Book and show have different endings. Plots were a little different too. Just finished the show. Liked it very much, but found it unsettling. A few “good guys”, but wow...different feel from almost everything else. I read that the author basically used random chance ( the I Ching) to decide what happened to characters.
There has to be a second season. This show was good enough to turn Amazon into a “TV Network”
With the way it ended I don’t know how they could have a second season. It was a great series but, like you, I found it “unsettling”. There sure were a lot of characters to hate...