Any ending, as long as it's well told, will be acceptable.
Personally, I have no expectations about “how this story should end” — just like with any book, I let the author guide me to the conclusion. Because how else is it supposed to work? It’s not my story — am I supposed to decide halfway through that it has to end a certain way, and if it doesn’t, what then — be disappointed?
Return the book and demand a refund and compensation for emotional damage and wasted time?

Personally, I have no expectations about “how this story should end” — just like with any book, I let the author guide me to the conclusion. Because how else is it supposed to work? It’s not my story — am I supposed to decide halfway through that it has to end a certain way, and if it doesn’t, what then — be disappointed?