There will be social interaction (highlights on kind 30041 and kind 1111 comments on 30040, probably) in Alexandria, but no main feed. The focus is on the books, the people reading the books, and the people publishing books. No random chatter.
Bookmarking/favoriting with ⭐, tagging and labeling, profile pages for npubs (showing their highlights, favorites, communities, and comments), bookmarks, book clubs, timed/scheduled reading, recommendations from your WoT, navigating and perusing the library, publishing to different formats like ePUB, that sort of thing, will be the emphasis.
More like Readwise, than Facebook.