It is a MagBook, not a monthly magazine, hence the higher price. Magbooks are designed to stay current longer than magazines and have much less advertising.

(Please excuse the clumsy URL)

http://www.magbooks.com/mag-books/computers-and-apple-technology/the-ultimate-guide-to-windows-phone

(Disclosure: Magbooks are from Denis Publishing - who publish PC Pro for whom I write a monthly column, and I wrote several chapters of the Magbook on Office 2010.)