Adam Bosworth explains why, even though I spent the only dollars I've ever spent on a computer book on an XSLT book, it was probably wasted money.

This is the paradox: XML was chosen in part because humans could read and write it, unlike the highly efficient babel of binary formats that preceded it. Yet languages encoded as XML grammars and used for manipulating XML can only really be read and written by programs (and a few very smart people). This is why books for XML and Java and books on XSLT sell in such great numbers. In making the formats easy and interoperable, we made the programming hard.