Rev. Marx has posted the final installment of his Necronomicon build log. You'll find the first part here, and the second over here. If you're considering making a prop tome this is one of the best tutorials I've ever seen, and Rev. Marx deserves a great deal of credit for documenting the process in such exhaustive detail. I have no doubt that it's going to become one of the go-to resources for Lovecraftian prop makers.
What makes this work is the distressing. The ragged paper of the text block, the wear along the edges of the leather, and the corrosion on the hardware all combine to give a real sense of age.