The Non-Designer's Design Book has been a great help to me. I bought copies for my employees because it was easy to read and showed practical examples of how a few basic principals can radically improve your designs.
I actually think '5 Development Tips Every Designer Should Know' would be more useful. This is because a designer these days probably has to play with CSS and HTML, if not jQuery too.
A developer won't be handling the design themselves, but a designer might well be contributing some code on the front-end. And it's sometimes the case that such code isn't well (or consistently) formatted, or is too complicated, as writing code isn't the primary aspect of their job.
It's like poorly organised PSDs. You might be totally fine littering your file with spurious layers, bad names, and inconsistent groupings. The person you might share it with won't feel the same way, and it'll compel them to waste time figuring it out and possibly spend more time making it sane.
But for personal projects where a developer might want their own site, the advice here is good.
How many "Why everyone should learn to code" articles show up on Hacker News? The same idea applies to design thinking. It will make you more powerful. User centered problem solving methodologies and visual communication abilities will help you with much more than side projects you can't pay someone to skin.
Good , but design is about culture and practice , like code is about process and practice. Want to be a designer ? get a generic art history knowledge , learn to use a paper and a pen, and just practice.
So is design. If you keep just practicing, you won't improve (significantly). If you practice, seek for constructive feedback from peers, and keep reading (theory of colors, etc) - you will improve a lot. Just like in any other area. No need to undermine the efforts that takes to become a good designer.