Ao3 Series Downloader von Sean Z Writes

Archive of our Own is an amazing fanfiction website, and they make it easy for users to download stories so they can read offline. However, their website doesn't offer an easy way to download an entire series.

This add-on adds a single button "Download Series" to any Ao3 series webpage (while logged in), that automates the process of downloading each of the fanfics included in the series.