For learning another tongue, relatively simple and light fiction is best. I recommend something like the Goosebumps series or the Harry Potter books. Or something like
Geek Mafia, available freely online. If you are feeling adventurous, try the English translation of Paulo Coelho's
The Alchemist; the themes can be a bit complex, but the language is fairly simple and the book is entertaining. Or if you like dystopias, try
The Giver by Lois Lowry. Once again, simple language, slightly complicated ideas.
Also, in reading books of the language you wish to learn you have made a good choice. Trust me, English is my second language as well.