Length of HBP (Possibly) Revealed
Thanks to TLC for pointing out that Amazon’s US library binding version of Half-Blood Prince is listed as having 672 pages. The book is still being edited, so there is no way we can say this is official yet. But we learned the number of pages in book 5 a month after learning the release date.
Update: As it turns out, Barnes & Noble is also listing the page count as such.