My favourite Hindi book (apart from Premchand's works and poets like Sahir Ludhianvi etc) is actually a translation of Hans Anderson's Stories and Fairy Tales, translated by Uma Pathak.
Another excellent source for Hindi literature are NCERT Hindi textbooks for classes 6th to 10th (didn't have additional language apart from English in 11th and 12th), and you will find fantastic authors and poets in there to start you off on Hindi literature. Good luck and have fun!