Sentences like these are very common with novels (fiction books) in English.
In colloquial English, and in spoken English for that matter, it´s possible to make questions by changing the intonation (how a word or words are stressed).
As explained here with "we´re going" vs "were going?"http://rachelsenglish.com/questions-vs-statements/
That was a touchy subject when I took an English course, my teacher was a stickler for grammar as per books, and I always enjoyed reading such books. When I tried to use some colloquial words with the speaking classes she went ballistic, she used to say that it was wrong!
Maybe it was that she wanted to teach a bit of academical English, and then we would learn slangs and informal ways by ourselves. But not on her classes...