Although buying books in a bookstore is more enjoyable, often time it is not more efficient than buying them online. Since I use kindle, I prefer to buy books online. Reading books with kindle is more practical and relaxing. I find it easier and more flexible while reading in many positions like while lying on the bed. It also good because of the letter size change feature and inverse mode that kindle has.
Amazon books now mostly have two version, thus kindle and the printed version.