Thanks for doing this - this seems like a very good addition to improve the retention of the information intake for books. At least for me - I've noticed that resurfacing what matters to me within a quite short timeframe after reading it, definitely improves how easy (or hard) I find to apply the key takeaways of a book after I've read it.

Tried to sign-up using Amazon, but got an HTTP 500 in the auth callback: /accounts/amazon/login/callback/