Glitches is an excellent short story to accompany The Lunar Chronicles. It features Cinder when she is a very little girl and and shows how she came to be a part of the Linh family. We see her meet her step father, step mother and sisters for the first time as well as see how hateful her step mother is even right from the get go. Pearl it seems has always been an angel to her - and I wouldn't have expected anything less. 
 It's painful to see how she is treated. Even in the beginning she knows she is different and doesn't quite belong. We also see how her step father disappears from the picture from the illness. Luckily she finds out quickly that she has a skill with tinkering on mechanical things and its a thankful thing she did otherwise I can't even imagine her having made it as long as she did in that family. 
 I wouldn't recommend this being the first thing you read in The Lunar Chronicles. If you haven't read anything in the series at all, start with Cinder, then it would be ok to read Glitches.