I was stuck here too, until I started checking the book cases on the north wall. Theres no little sparkles to tell you where they are, but I found a book Lily hadn't finished. After reading it, Lily made some kind of comment about coming back to study more. After that I went home to change into my casual clothes for gardening. Lily says something about finding an old skimpy outfit and wearing it to the library next time.
You mean theres nothing more to it?