Harry Potter and the Order of the Phoenix (spoilers behind cut).

I read the fifth Harry Potter book Saturday evening, finishing at 3AM Sunday. It took me a while to sink into - I think because I'd put Jo Walton's The King's Name down to read it. Jo's writing is so very good at the sentence level, and the protagonist's voice in The King's Name is so spare and distinctive, that the clunkiness of Rowling's prose irritated me quite a bit in the first several chapters. But then, fortunately, I got sucked into the plot.
( read more - including vague spoilers. )