Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Inflexible device

My friend purchased this only to find that the only books it works with are from Amazon. Why would you pay this much to buy a implement that only does books from 1 source?No end of frustration setting it up and trying to figure out if you can use with the the local public library (you can't).Do not buy this device, get something that has some market flexibility.