Which is better, ChatGPT or Perplexity, for discussing a book?

For open-ended discussion — explaining themes, debating an argument, generating discussion questions — ChatGPT is the stronger conversational partner. For checking whether a specific factual claim in the book still holds up against current sources, Perplexity's citation-backed web search is the better tool. They are built for different jobs rather than competing at the same one.

Can NotebookLM read an entire book?

Yes, as long as you can upload a clean digital copy (PDF, text file, or similar) within its file-size limits. It answers only from what you uploaded, with citations to the specific passage — which makes it the most accurate of the three for a specific edition or a niche title, but only for books you can actually get into digital form and upload.

Does ChatGPT know about books it hasn't read?

ChatGPT does not "read" a specific book in the moment — it draws on patterns from its training data, which includes enormous amounts of discussion, summary, and criticism of widely-read books. For popular titles this can look like real familiarity with the text. For niche, recent, or self-published books with little written about them online, its knowledge thins out fast, and it can produce confident-sounding but incorrect details.

Is Perplexity accurate for fact-checking nonfiction claims?

It is meaningfully more reliable than a tool with no live search, because it shows you the sources it used rather than asserting a claim from memory. It is not infallible — the sources it finds can themselves be wrong or contested — but the citations let you evaluate the claim yourself instead of trusting the AI's word alone, which is the core advantage over ChatGPT's uncited responses.

Should I use one of these instead of a dedicated reading app?

For a single discussion, a one-off fact-check, or a deep dive into one document, any of the three can be genuinely useful. None of them track your reading across a book or a library over time, resurface what you are about to forget, or turn your highlights into a review schedule — that is a retention problem, not a discussion problem, and it needs a tool built around your reading history specifically.

ChatGPT vs Perplexity vs NotebookLM for Studying Books

ChatGPT vs. Perplexity vs. NotebookLM: Which AI Should You Use to Study a Book? Quick Answer: ChatGPT, Perplexity, and NotebookLM are not interchangeable for book study, even though all three can "talk about a book" with you. ChatGPT is the best general-purpose discussion partner and is strongest when you want it to explain, connect, or quiz you on ideas from memory of its training data. Perplexity is the best choice when you need a claim checked or sourced against the live web — it cites what it finds, which matters for nonfiction arguments and statistics. NotebookLM is the best of the three at staying grounded in one specific text, because you upload the actual source and it answers only from what you gave it, with citations back to your own document. None of the three were built to track what you have already learned, resurface it before you forget, or quiz you without you asking — that gap is what a dedicated reading tool like Chapterly is built to close. If you have tried discussing a book with ChatGPT, checking a claim with Perplexity, or dropping a PDF into NotebookLM, you already know these tools do not behave the same...