Oh, wow. We just got the first PDF proofs in, using O’Reilly’s house style. There’s no index yet, and we still have a chapter to add, but we’re already at 536 pages. The final number will thus be somewhat north of this: maybe 550 pages, instead of the 450 we thought as recently as a day or two ago.
Update: Don noticed that several chapters were missing from the PDF. I’ve fixed this, and now we have 666 pages in the current PDF. As a result, the final count looks like it will be near 700 pages. That pretty well blows my mind.