Gemini Notebook (formerly NotebookLM) Asking questions of your own series bible and previous books for continuity. Free to try; paid plans listed on site
Otter.ai Dictating scenes or transcribing interviews and voice memos. Basic free; Pro $16.99/user/mo ($8.33 annually); Business $30 ($19.99 annually)
Perplexity Quick, cited research for historical or technical details. Price: see official site