NotebookLM has been one of the more useful projects I've used. Being able to focus a language processing model directly to the content you're looking for is really useful. I currently support a data application where the vendor's documentation for it is not particularly well organized. It's spread across dozens of PDFs, sometimes without particularly well reasoned organization. Dumping all those PDFs into NotebookLM…
The mind map feature is also handy, although last I used it, it was a bit clunky to export.