I'm not a designer, so I'm probably not the right one to ask - but for what it's worth I think that it is like everything else in life: a little talent and a lot of work will get you the experience needed to do good design.

When I work with designers I notice that the finished result is often very far away from the initial idea, and that the intermediate steps are obviously experiments in some direction. It is apparent that a lot of time goes into trying things out that are never seen in the finished product. It's probably a lot like writing essays: write a lot and throw away the 90% you don't really need.

So in short: I think there are no shortcuts, it's about experience and hard work.

If I had to expand my list, I would include:

"Design of Everyday Things" by Don Norman "The Visual Display of Quantitative Information" by Edward Tufte "Don't Make Me Think" by Steve Krug

Tufte will give you the vocabulary around visual concepts. Norman will give you the vocabulary around evaluating basic usability. Krug will apply both to the domain of the web.

Additional recommendations: About Face 3.0 -- written by the head of Cooper Design, it outlines in somewhat dry fashion the frontiers of user experience process. Buy this only if you're desperately interested in becoming an interaction designer, or you want to institute user-centered design in your organization. It's really the UCD bible.