The book is exclusively about the 15c stamp and was written by Bill Weiss. It is more detailed than the site for this stamp.
There is also more info on the site if you poke around, you can find more info in the library section. http://www.stampsmarter.com/learnin...earning.html
Examples include this article on Large Bank Notes; authors are Bill Weiss and Scott Payton.http://www.stampsmarter.com/learnin...eIssues.html
The Stamp Smarter 1847 content was originally written by Bob Allen but has been amended over the last year or two.