Bookworm Puzzle

A bookworm eats from the first page of an encyclopaedia to the last page. The bookworm eats in a straight line.

The encyclopaedia consists of ten 1000-page volumes and is sitting on a bookshelf in the usual order. Not counting covers, title pages, etc., how many pages does the bookworm eat through?

(I found/stole this one from rec.puzzles some time ago - look it up if you like, but it's better to try and figure it out!)