This is such an important book. It should be studied in primary (and probably secondary) schools, if only for the sake of the Melissas in the world. 
 But its subject matter is not the only good thing about it, far from it. 
 It's very well written, using simple language while perfectly able to convey emotions. We feel for this little girl, we cry with her, we're happy when she's happy. Every little hope, every little joy. And it's wonderful. 
 In the same way, the story is simple, as simple as other stories for kids. But it's perfect as it is. 
 A very important book indeed. 
 (And now, I really need to go read Charlotte's Web)