Amazon are one of the most recent companies to enter the music streaming market. At the time of writing they have over a million songs and hundreds of playlists. At first this seems poor compared to the more established players in the world of music streaming who boast over 30 millions songs in their premium services.
However Prime Music is in its infancy and is only going to grow as time goes on. In the mean time it's worth checking out what they do have in the million song library. As always ensure that you cancel before the end of the free trial period should you not wish to continue on a paid subscription.