It was probably only 4-5 hours of reading a day, on average. I did still work, but didn't do much else on some days!
If it's the kind of book where I can't wait to find out what's going to happen next, and especially where I already know the characters, I read really fast. I did the same thing with each of the Harry Potter books -about 8 hours each even for the big ones. Some people think that reading it so fast diminishes the experience, but what I end up doing is re-reading them (non-sequentially) for quite a while afterwards. I get the initial rush of getting carried away with the story, but I also get the enjoyment of all the little details afterwards. When I read the first few books of the Kushiel series by Jacqueline Carey, it was 2 months before I could tear myself away and read something different!
I have to rest now, though, and read something intellectual - all about gene splicing and natural selection. Happy Birthday Charles Darwin!