I have bought a lot of books over the years, and this one is easily one of the best.
It contains a beautifully open ended plot, with so many different versions, twists, turns and possibilities that I think I coudl run it again and it would be completely different. There are piles of NPCs, all with at least two versions of themselves, excellent (and I mean EXCELLENT) resources and hand outs. The key to Cthulhu games for me is props, and I think these really made the chronicle fly.
I copied them out by hand, but the copy came with a link to a PDF colour version of the files, which are excellent.
The whole thing blew my mind as far as the possibilities went. You could use it straight as a play guide and plot or you can take it and run with it, building your own story around the frame.