I own a few. I also own some from Addison Wesley, Prentice Hall, Morgan Kaufmann, etc. For example, "XML Schema" by van der Vlist is just incomprehensible (I don't understand how it got passed the editor). Plus the author is by no means an expert in XML Schema. That's actually the gist of the problem with O'Reilly books: they are written by non-experts and the editorial work is poor.