What are some alternatives?
When comparing Barnes & Noble NOOK Books and regular expressions 101, you can also consider the following products
Kobo Books - Kobo Books is a best in the class eBooks and eReadering apps for many reasons.
Expresso - The award-winning Expresso editor is equally suitable as a teaching tool for the beginning user of regular expressions or as a full-featured development environment for the experienced programmer with an extensive knowledge of regular expressions.
eBooks.com - eBooks.com is a leading retailer of ebooks, with a vast range of ebooks from academic, popular and professional publishers.
RegExr - RegExr.com is an online tool to learn, build, and test Regular Expressions.
Harlequin - Harlequin is a bookstore that sells paper books as well as eBooks. The store mainly deals in the genre of romance novels.
Regex Hero - Online Silverlight regular expression tester with instantaneous highlighting, C# and VB.NET code generation, code completion, regex analysis, benchmarking, and more.