Kevin Maney points out that, unlike books with their varied and descriptive covers, e-Reader devices conceal the identity of what you’re reading:
…the Kindle lets readers down with respect to one subtle but powerful element of the traditional book’s appeal: its role as an identity marker. Pulling out a particular book on an airline flight or in a doctor’s office can mean staking a claim to being a particular kind of person. Likewise, the books lining your living room or office can tell others about your interests and background. But on the Kindle, no matter what you’re reading, all anyone else will see is an unchanging plastic device.
(Via Clive Thompson)