If you're a voracious reader who's just gone digital, you must be loving the convenience of having all your books on you at any time, along with the extra features such as search, definitions, and highlights. Whether you're using an e-reader like the or you're reading books on your phone or tablet, there are a lot of things to love, most of all the fact that it has also become incredibly simple to buy the books you want to read. Devices and apps all come with their own marketplaces, and it's pretty easy to rack up a big bill quickly.