[bstpierre]

Two main things I use it for:

1. Keeping track of where I am in a series. Goodreads has a handy feature where you can see the list of books in a given series. I maintain a reading list with (way too many) different series and it has my next book in each one.

2. Remembering which books I've read. (Kind of related to #1.) More than once I've gotten more than a few pages into a book and realized, "hey I'm pretty sure I read this before".

Either of these would work in a notebook or spreadsheet but that would require changing my workflow (and "importing" a long list of books).