To browse the contents of a book, use the CONTENTS / TOC button from any recipe or book home page.
Right now it is easiest to read a book on a desktop web browser, or in landscape mode on an iPad or tablet, as this lets you keep the TOC open as your browse through the book.
You can use the previous/next buttons to move to the next recipe or section, and if you are using a keyboard you can also use the left and right arrow keys to skip through the book.
Future planned improvements to browsing include:
the ability to "swipe" to the next and previous recipe on touch devices
a streamlined "read mode" reducing distractions, and allowing you to focus on the content of the book rather than additional links