I love this idea! One of the main use cases I would like to see would be sharing a direct link to a collection. It would be nice to be able to build a collection and link directly to just that collection. Additionally, having the ability to add a public description for each book in a collection would be really nice since you could use that to provide additional context.
Linkable book shelves: Noting this! We'll prioritize Description for a book: Right now, there's a kind of hack you can do: if you write a "thought" about a book, it will show up on your book page too. We're thinking about some kind of "pin a thought as a description" feature -- that should be on it's way too!
Here's to iterating : )