Book about friendships, loss and redemption

Ok, this is a bit specific… but I basically want a ‘break up’ book that is centred on friendship rather than romantic love.

Does anyone have any recommendations?

Ideally, I’d love a story where people repair and reconnect after estrangement… but I am open to other stories (fiction or non-fiction) of how people deal with the loss of a friend (not through death).

I hope you can think of some good ones. THANKS!!