Mark Summerfield is a computer science graduate and qualified teacher with many years experience working in the software industry, primarily as a programmer and documenter. Mark owns Qtrac Ltd., http://www.qtrac.eu, where he works as a programmer and where he created and now maintains his commercial software --- PDF comparison tools DiffPDF and diffpdfc, and for book indexers, XindeX.
All Mark's books are aimed at programmers and others, such as students, scientists, and engineers, who already have some programming experience (how much depends on the individual book). Each solo book has its own page on the Qtrac website from which the source code can be downloaded and that lists the book's errata. All the books are designed to teach technologies that Mark loves and has found to be the best of their kind.