After releasing Windows 8.1, Microsoft has made product guide for it available on its download center which gives in depth tour of new and improved features in Windows 8.1 and Windows RT 8.1.

Windows 8.1 Product Guide available for download in PDF format containing 49 pages with file size 10.2 MB covers " the great selection of built-in apps, the powerful set of cloud-based services and entertainment, and better ways to connect and find and discover, along with the exciting Windows Store app marketplace, and the many ways you can personalize your experience to sync with your life. It also includes a glossary of touch-based gestures and walks you through popular usage scenarios so you can see how Windows helps you have more fun and get more done. "

Windows 8.1 Product Guide PDF

You can download this from here.