Ruby Cookbook PDF

O'Reilly is now selling the Ruby Cookbook as a downloadable PDF for 50% off the cover price (see the "I want the PDF" checkbox in the upper right corner). Seems this is the first full-length O'Reilly book to be sold as PDF. PDF copies of the Cookbook will be watermarked but not encumbered by DRM. There is also interesting Ruby Cookbook Official Unofficial Homepage with book source code, tests etc.