I just bought Agile Web Development with Rails and Programming Ruby as PDF directly from the pragmatic bookshelf. I already have the dead tree version of Agile Web Development with Rails, but I like reading on the screen and the convenience of a library of useful stuff on my harddisk. The PDF are neatly hyperlinked, the code examples are color highlighted and the formatting works well for on-screen reading. It's clearly not what they just happened to prepare for printing anyway, but a genuinely value-added version at just over half the price of the paper version.

If I should find an error in the Rails book there's a “Report erratum” in the footer on each page linking to a webpage showing the errata already reported for that page and a form to add your own errata. Unfortunately there's not the same feature for Programming Ruby.

Best of all there's absolutely no DRM in the files I downloaded, just a footer on each page which says “Prepared exclusively for Morten Liebach.” Thank you very much, best copy protection ever!