I searched the thread, but could not find it.
Not quite a book, just a short story serialized over 6 chapters, but I found H.P. Lovecraft's "Herbert West: Reanimator" not only very good, but also one of the very first depictions of zombies in fiction, despite not being called that nor them being particularly fond of brains as opposed to general flesh.
Like most Lovecraft, it focus on psychological horror through subtlety, not gratuitous gore as I suppose most zombie books are about.
The story is in public domain and available for free among many others in a
superb Lovecraft collection here at MR. MOBI also available
here.