It's not a revolutionary update, but the new sharing functionality for notebooks is certainly a welcome change given that previously you could only publish notebooks to the web for manually sharing a view-only version.
Evernote sharing is made available through a new sharing tab on the web. This will open the sharing settings menu, where you can adjust settings for each of your notebooks, and view quick links for currently shared notebooks. From here you can opt to share notebooks with the world, or share with individuals via email. When sharing with individuals, you can now specify if these recipients can just view the notebook, or can actually add and edit content.
There are a few caveats to shared notebooks, however, given that Evernote is trying to push their premium accounts. So as a free user, you can share with the world (that feature already existed) and view or edit notebooks shared with you, but you won't be able to take advantage of the new share with individuals feature. Only premium users can invite collaborators to edit notebooks. Also keep in mind that shared notebooks can only be modified on the web, and currently there's no way to track who's making edits.
Watch the video below for a quick demo: