Is NotebookLM the best tool to summarize dozens of large PDFs strictly based on the files?

I need to summarize several large PDFs. My goal is just to get a brief overview of what each specific case is about.

I was thinking about using Claude, but I noticed that both Claude and ChatGPT often use external internet knowledge or extrapolate, instead of strictly sticking to the provided text. I need a tool that relies 100% and exclusively on the PDFs, without adding outside information.

Given this, is NotebookLM my best option for this task? Thanks!