Since you ask for something simple i could not recommed any other book more than "The little Prince" By Antoine du Exupéry, for me it might the best book ever written and very light and easy to read, can be read in 2-3 days easily.
If you want something a bit more complex yet entertaining i advise any Sherlock Holmes book, you can read "The Scarlett study" wich is the first one, or you can try something like Harry potter that even if you already watched the movies adds a lot of details, if you dont might getting a bit politic Animal Farm is another great advise.
I'm not the most avid reader myself, so dont take me for some kind of expert, but i really enjoy it i hope i gave an interesting suggestion.
By the way all this are relatively short books, except the lastest Harry potter books, and some are even public domain.