Everyone should read Mark Pilgrims thoughts on E-books as it explains why DRM just doesn’t work.
With books especially, the ability to share is precious.
John Gruber also points out the problem of longevity:
Barring physical catastrophe, I expect that the real books I own the ones printed on paper will remain in good condition long after I am dead.1 With digital Kindle books, Im not even sure theyll be available 10 years from now. Theyre only useful so long as you own Kindle-compatible hardware. What happens to these e-books if Amazon, having lost money on the endeavor, stops producing Kindle readers a few years from now? What are the odds that these files will be readable 50 years from now?
DRM protected e-books? No thanks.