Not only is Esperanto an easy language to learn, but there are also lots of free resources online. Project Gutenberg has a lot of Esperanto books available. They not only have a lot of good textbooks and teachers, but also fiction translated into Esperanto. My favorite textbooks are below.
Additionally, Lernu.net is a great resource online for learning Esperanto, as well, so give it a look if you want to learn Esperanto.