I recently started reading Middlesex by Jeffrey Eugenides, the Pulitzer Prize-winning fictional story of a hermaphrodite. The reason I did so, other than being unable to get into the classic Of Human Bondage by Somerset Maugham (at which point I should mention I grew up on vicar-laden English novels), was because my sister left the book with me during a recent visit.
She buys her books at Costco for three reasons:
1. The wholesaler consistently carries award-winning books.
2. The books are offered in paperback, which compared to hardcovers, is often less than half the cost, not mention easier to transport, especially in this new era where airlines not only charge passengers for each bag they check, but are also probably contemplating fee increases based on a person's weight and amount of bellybutton fluff.
3. Since the books are more affordable, my sister can take her time reading without having to worry about returning the books to the library by a specific date, and if she forgets, paying a fine.
I, too, am a fan of the paperback format for the above reasons, though if you want a few more arguments for why writers should push for the publication of their books in soft cover, read the Holt Uncensored article titled Stop Starting With Hardcovers.