Cross-Book Synthesis
How to connect highlights across books
You highlight the best passages as you read — then they sit in a notebook, one book at a time, and the connections between them stay locked in your head. Here’s how to surface them.
The short answer
To connect highlights across books, group the books into a collection and let a synthesis layer surface where they agree, disagree, and build on each other — grounded in the passages you actually marked. Syntopica does this across your imported Kindle highlights: semantic search assembles the relevant passages from every book, and every citation links back to your own highlight.
Why highlights stay siloed
Most tools store highlights the way you made them — per book, in the order you read. That’s fine for review, but it hides the thing that matters most: the moment a passage in one book answers a question raised in another. The book on habits echoes the book on neuroscience; the biography confirms the philosophy. Held in your head, those links survive for a day. On the page, they need a way to find each other.
How cross-book synthesis works
Syntopica makes the connections findable in three steps:
- Import once. A Chrome extension brings in your Amazon library and your Kindle highlights — text, notes, location, and chapter.
- Index by meaning. Your highlights are embedded and clustered semantically, so passages about the same idea group together even when the authors use different words.
- Ask across the collection. Pose a question and Syntopica assembles the relevant passages from every book, showing where your reading agrees and disagrees.
From connections to a synthesis you can keep
Once the connections are surfaced, you can build a collection around them, chat across it, and export a syntopical brief — a structured synthesis of themes, disagreements, and open questions you can save or share. Every claim stays grounded: each source is labeled, and every citation links back to the highlight you actually marked, so the synthesis is yours to verify, not a summary to take on faith.
Frequently asked
- How do I connect highlights across different books?
- Group the books into a collection, then ask a question across the whole collection at once. Syntopica searches your highlights semantically, assembles the relevant passages from every book, and surfaces where your reading agrees, disagrees, and builds on itself — each answer grounded in the highlights you actually marked.
- Can I search my Kindle highlights across all my books?
- Yes. Syntopica imports your Kindle highlights and indexes them with semantic (meaning-based) search, so you can find related passages across your entire library — not just keyword matches inside one book.
- How does Syntopica find connections between books?
- It embeds your highlights as vectors and clusters them by meaning, so passages about the same idea surface together even when the authors use different words. You can let it suggest theme-based collections automatically, or build your own and ask questions across them.
- Will the connections quote my actual highlights?
- Answers are grounded in the passages you marked, each source is labeled (your highlight versus broader knowledge), and every citation links straight back to your own highlight so you can verify it. Where an answer draws on knowledge beyond your highlights, it says so.
- Does this work if I have thousands of highlights?
- Yes — that is exactly the case it is built for. The more you have imported, the more cross-book connections there are to surface. Syntopica was validated on libraries of thousands of books and tens of thousands of highlights.
Surface the connections in your library
Import your Amazon library and Kindle highlights free. Get reading guides for every book and synthesize across everything you’ve read.
Free during beta, no credit card required.