Mandarin Companion offers a series of graded readers for learners of Chinese. I haven't read all of them yet, but the two I have read have both been great. Considering that they use a very limited number of characters and words, they still contain interesting stories that don't feel as stilted and boring as most textbook dialogues. You might not want to read these solely for literary pleasure, but they are the best graded readers I know of and far more interesting to read than textbooks.