TOC should be also displayed for early release books.
Python for Data Analysis
Agile Tools for Real World Data
Thanks for writing us about this. Your comment has started a discussion about this, and we're looking into adding TOCs for Early Release books.
In the meantime, you can see the current TOC and preview some of the contents for this book on Safari Books Online at http://my.safaribooksonline.com/9781449323592?portal=oreilly&cid=orm-cat-readnow-9781449323592
Hope that helps!
Thanks again for your feedback,