Books about relationship ambiguity, losing self in marriage, etc...?

[Alcemeg]

Hello folks -- I just wanted to know if anyone can recommend any good books that deal with being unhappy in a long-term relationship but having trouble working out the way forward.

My Googling/Amazon skills can't be that great because there must be some excellent reads about this sort of thing, I just haven't found them yet!

Thought of another- Blood Orange

Thanks everyone! I am still not quite finding the sort of book I'm writing... beginning to think there's a reason no one has written the book I'm writing, as it just may not tick all the boxes for thrills and spills!