Yes, you can download it, it works and you can start playing with it, however it is a “Preview” (Back in the old days we used to call it BETA)

There are also a bunch of documents you can read to understand all the new features (trust me, there are many new things)

• Windows 8 Consumer Preview Product Guide
  Download a detailed guide to the new and improved features in Windows 8 including AppLocker, BitLocker, Windows To Go, measured boot, and Client Hyper-V.
• Windows To Go Technical Overview
  Learn how Windows To Go can help you provide users with bootable USB storage devices containing a copy of Windows 8, along with their business apps, data, and settings.
• Frequently Asked Questions: Managing the Windows Store
  Get answers to frequently asked questions about managing end user access to, and usage of, the Windows Store within your organization.
• The Windows 8 User Experience
  Learn more about application, Web, and cloud features for end users.
• Windows 8 Consumer Preview Technical Forums
  Get help with questions on installation and setup, networking, compatibility, security, performance, and more.

You can read more of this here:

http://technet.microsoft.com/en-us/windows/hh771457.aspx

The download link is here:

http://windows.microsoft.com/en-US/windows-8/iso?ocid=W_OFF_W8P_TechCenter_ISO_EN-US

If you need the ADK, you need to have access to MSDN to be able to download it