Not much has changed in email coding since the 1990s, unfortunately, so the book won’t be out of date. There is some scope for @media etc. these days, but not much.
The author works for CampainMonitor, an email sevice that has a ton of articles and resources for creating HTML emails, so that’s a good site to visit. Their rival, MailChimp, also has great articles and other resources. And there are many, many other online resources. You just need to do some basic googling.
My post was prompted by the book, in particular changes to technologies. For example it refers to Outlook 2007, but we now have 2010 and 2013: four years in IT is a long time.
I am looking for information that updates relevant topics in the book, which addresses primarily the creation of emails (both HTML and text) but also refers to marketing in a wider sense.