I have read a couple of chapters of each of those books, the HTML & CSS I more jumped to the sections I wanted to read and covered more chapters as there was less detail to learn.
I discussed the use of WordPress’ own database system with two of my friends who are choosing to use WordPress. I have considered using Joomla or Drupal instead and am still making my choice. WordPress can be used for an e-commerce site, however it is generally used for making blog sites, information sites and other fairly non complicated sites. It is very easy to use, but looking at the specs there could be some constraints at everything seeming to be in a WordPress environment, with WordPress plugins and WordPress tools etc etc.
Joomla offers perhaps more of a challenge in installing it and getting going, but seems to have more possible components that are independent to the CMS. This could lead to more specific / advanced components being used to create an e-commerce site.
Both CMS’s have communities of followers and documentation, with WordPress being by far the biggest.
I also looked at Magento and OpenCart – these are both very good open source options. However there are a bit too “turn-key” as one of them described themselves, it looks like it would be easy to get going – but a lot of the technical detail may have already been taken care of. It’s certainly worth installing one of these to take a look though, which I plan to do soon.
Therefore the biggest risk I face at the moment is which CMS I am going to use, as then the tools I use following this depend on this choice. The reduction in risk will have to be further research, discussing choices with my colleagues and trying to install some of them to try (or using demos, I already played with the OpenCart admin and customer facing demo).