You either read that title and thought “what’s .epub?” or thought “Finally!” and did a backflip.
That leaves me in a weird position.
If you don’t know what it is, you probably won’t care much (i.e., you likely don’t have a massive collection of .epubs that you’ve wanted to use with NotebookLM).
And if you are really excited about it then you probably haven’t even read this far because you are already in NotebookLM trying it out.
Oh well, I will press on and keep it short so that you can go and “play”.
There isn’t anything different with the process of adding .epub sources. Just go to notebooklm.google.com, open a notebook, click add source
Now, epub is in the list (hover over and more)
Add your file(s), and you should be able to chat or create artifacts from it