回复：Amazon Kindle ?

Yes, you have to buy e-books.  Most of the time it's a little cheaper than the hard copies.  But some books especially classics are free at Amazon Kindle Store.  Also, you can find many websites that help you download books for free.  Our experience is to get a 3G version if you trevel a lot.  If you only have Wi-Fi, you have to have internet access to download.  If you have 3G then you can do it through 3G service when you are in remote/rural areas.  Both Wi-Fi and 3G are already included in the purchase price and are thus free.