I think many books are worth $40. It depends on the quality of the writing, and for computer books/manuals about artist software, the quality of the artwork, layout, and screenshots. I would pay $40 for a glossy paper, high color book that had lots of good information and was written well. Preferably with a CD. I will NOT pay $40 for a thin papered book with 8 pages of glossy photo inserts, with the rest of the illustrations in fuzzy greyscale.