I think most of the books can be purchased in E-Book format, for example:
http://www.wiley.com/WileyCDA/WileyT...764578472.html
The E-Book does cost as much as the printed version however. You may also want to take a look at
http://wrox.books24x7.com/ which is the online Wrox Library and allows you to view all of the books on there in their entirity for 50USD per 3 months.
hth.
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