FWIW, I have already preordered the book. However, I just read "Appendix A" (a.k.a Intro to Boost.Preprocessor) and if the book comes anywhere close to explaining MPL like the appendix explained PP, then I am ready to spend Christmas vacation outside on the porch reading the book (yes, I live in the south, where, for the most part, shorts and Christmas coexist quite nicely). Nice job! I had previously tried to read the PP docs, but first impressions found the initial hump just way too time consuming to even give it much effort. However, the intro is a wonderful start for anyone (though I still wish there was more). I feel like I have had a peak at the man behind the curtain, and it's not so much voodoo (though I am sure the implementation is quite formidable). Anyway, thanks for the very well written doc, and here's hoping that the book makes it to press on the new date (Dec 17, 2004).