I was pleasantly surprised to learn recently that almost eight years after buying a PDF eBook version of XML pioneer Ken Holman’s book Practical Transformation Using XSLT and XPath, I am now entitled to a free upgrade to the thirteenth edition, which covers XSLT 2.0 and XPath 2.0. While it’s not the first book I’d recommend to an XSLT beginner (keep in mind that I’m biased), it’s an excellent reference work.

Ken also published this and his Definitive XSL-FO as bound, hardcopy books in the same Prentice Hall Series as my XML: The Annotated Specification. I asked him how well his decision to sell PDFs of his XSLT and XSL-FO books online directly to his customers had worked out, and how it compared with his experience with the Prentice Hall version. The following is his response.

The decision to go to paper was secondary. The primary decision was to go electronic so that we could offer the perpetual free updates to all future editions. Specifications don’t move that quickly, but how people use specifications does evolve and mature. The first 12 editions of the XSLT book only covered XSLT 1.0, but the editions reflected changing practices. Customers of the first edition in March 1999 have just received their 12th free update to the 13th edition which now includes all of XSLT 2.0. We just published the 7th edition fo the XSL-FO book which now includes all of XSL-FO 1.1.

As a user of specifications I figured any paper book I would buy would be out of date before long. I didn’t want my book to have that experience with our customers. The perpetual purchase is a feature of the electronic book that cannot be offered with the paper publication. Some peers have criticized our choice to make the updates free as a lost opportunity for revenue. Again, putting myself in my customer’s shoes, I didn’t want to be charged for updates since there isn’t any overhead in sending out an email notification of an updated edition. Our customers have appreciated the “live” feeling of always having an up-to-date publication for the cost of the original purchase. The more editions they get for free, the more cost effective their original purchase becomes compared to a paper book purchase.

The decision to go to paper was a favour to the series editor Charles Goldfarb who wanted to include the XSLT book in his “Definitive” series. Prentice Hall only has the print rights. And since the same document model was used for the XSL-FO content, it was a quick project to bring the XSL-FO book to paper in the same series. All other electronic rights and other uses were retained by Crane, and we are in the planning stages for new product offerings based on the same content, probably being announced late Q2'2008.

Another big benefit of the electronic PDF sale is the flexibility in licensing. We have worldwide staff licensees. These customers pay a one-time fee for the original purchase of the book and they mount the PDF files on a private intranet server for staff use only. We do not need to be informed of the number of copies that get used internally. These customers also get the perpetual updates to all future editions, they just retrieve and mount the revisions up on their servers. For a big example, all US Government employees of all departments of all offices around the world have perpetual access to the one staff purchase of each of the two XSL titles we have. We don’t know how many hundreds or thousands of copies may be being used.

One customer drawback to the electronic format is forgetting to inform us of email address changes. Announcing this last free edition revealed hundreds of dead email addresses, so there are customers out there who are due their most recent copy of the book but we can’t tell them about it. Hopefully they’ll come back to us in time and request their copy … we’d be glad to keep them up to date.

From a revenue aspect, we have received many many times more revenue from PDF book sales than from paper book royalties. And the PDF book sales are continuing while the paper book royalties have tailed off. There isn’t much market now for version 1.0 of these technologies, whereas the PDF books now include all of XSLT 2.0 and XSL-FO 1.1.