if you want to get the pdf of "Power Programming with Mathematica" without going to an ebook download site, it's directly available at
http://data.wolframmathematica.ru/working-files/WolframTechnologyCollection/books_mathematica/Power_Programming_with_Mathematica_The_Kernel.pdf
not: david was going to write a second companion book but he said he was so dissappointed ith the sales of his Kernal volume (which is IMO a very good book, though dated) that he decided not to do it.
additionally, if you want to see really neat WL programming code i recommend "Computational Recreations in Mathematica" by Ilan Vardi from 1991. (this was the book that turned me on to WL programmng) .