I don't know anything about AI but I've always wished I could just upload a bunch of documents/books and the AI would perform some basic keyword searches to figure out what is relevant, then auto include that in the prompt.
NotebookLM is currently free to use and was so good I almost immediately started paying Google $20 a month to get access to their pro version of Gemini.
I still think the Groq APIs for open weight models are the best value for the money, but the way OpenAI, Google, Anthropic, etc. are productizing LLMs is very impressive.