Harry Potter and the Goblet of Fire by J. K. Rowling, 734 pages
I've read this book before, more than once, and will read it again. I picked it up this time because I'm working my way through the series again to see if the books are age-appropriate for my youngest. She has read up through this one, and really wants to read the next one. But I'm making her wait until I've read it to double check just how dark it really was.