The closest word I can think of is a sycophant but that’s too strong word and not exactly what I’m looking for. The word I’m thinking of has negative connotations and it’s for someone who is friends with different groups but only at a superficial level and isn’t necessarily honest about who all they’re friends with. This person would be seen as untrustworthy.
In the book, the character was sincere. He really did try to see both sides and get along with people. It never seemed to work.
To answer the original question; a good term would be ‘two-faced.’ Someone who pretends to be a friend and then gossips about you with others.
‘Wishy-washy’ is a person who simply goes along with the majority without having strong opinions of their own.
I agree. I think ‘two-faced’ is the best i’ve seen based on OP’s various comments in the thread.