Serendipity is one of those "tech can't copy it" things often sited by people clinging to the-way-things-were.
And there is serendipity in libraries and book stores. There's a lot of fun to be had finding books. But that's only for people who have a wide enough reading palette to enjoy a variety of books. I think that most readers pick their books for comfort, so they're not really interested in discovery.
That's why bookstores are failing across the country, why Amazon's suggestion logarithms do more business than libraries. We just aren't interested in reading much.
And I wonder if the internet doesn't offer the deeply engaged reader as many opportunities for discovery as the book store. Sure, if you're ruling out every recommended read and every suggested title as unserendipitous, sure that doesn't leave much else. But looking at it another way, every book reviewer is a book seller.
I wonder if that isn't really better in the long run.