One way to internalize a book is by reviewing it. A full reread is often too much work, while a book summary feels sparse. So I built a new kind of reading experience called layered books for navigating a book at varying levels of abstraction.

The key idea is that you can choose, at a granular level, where to spend your attention. If a chapter seems unimportant, skip it. If a chapter seems important, expand its nested summary and maybe read the raw text itself.

A layered book has chapters at the top, key points in the middle, and details at the bottom. You click each unit to expand or contract its children.

As you read the overview, you can navigate to specific sections of the raw text. In the split view, the layered book is on the left and the raw pages are on the right. You can click parts of the layered book to navigate the underlying pages, like a table of contents.

There are other uses beyond review. You might chase an answer to a question that spans several books. You might judge whether a book is worth reading in full. You might copy the summary and give it to your favorite chat app. You might share a key point of a book with a friend via URL.

Initially I imagined that you would generate a layered book once and then everyone else using the website would use it for free. I think that has copyright issues despite the existence of Blinkist, Spark Notes, and Google Books. So the books you upload and their layered counterparts are available only to you.

Influences and further reading

• Dynalist - expandable outlines
• Video Navigator - my earlier project for navigating youtube videos using a summary
• Why Books Don’t Work by Andy Matuschak
• How I Read by Henrik Karlsson
• Chase Your Reading by Robin Hanson