Daddy Long Legs (1912) is about Judy Abbott, an orphan whose education is funded thanks to a mysterious guardian.  All the guardian asks is that she writes one letter to him a month.  Aside from the first chapter, Daddy Long Legs is the letters that Judy writes to her guardian.

Judy's letters are pretty funny and I like that she includes drawings to illustrate some of them.  Overall, this was a cute, quick read!