I was debating a 3 or 4 star but leaned towards 4 since that's the time to which I stayed up reading this (oops).
The vanishing half explores identity, belonging, selfishness, and guilt in some interesting and potentially uncomfortable ways. The book was quite character driven and slow (especially in the first third), which is always a strength as far as I'm concerned.

The central idea in the book is really about who and what create our identity, how much does identity hinge on others perceptions of us, and how much control do we have over our identity. I'd recommend it to anyone interested in exploring those topics.