I'm enjoying The Non-Designer's Design Book - (http://www.amazon.com/The-Non-Designers-Design-Book-Edition/...), as a guy who spends hours trying to figure out why my layouts look like crap, this book has really helped me get to grips with the basics. Which is tbh, where you need to start. After that, just keep reading, designing and failing. Dealing with the inevitable frustration is key (see educational mithridatism). Learning how to use a good design tool also helps a lot. I'm playing with Sketch which is pretty awesome.

I guess in the end, there is no real linear path to learning design. You just sort of have to bumble along until you find your stride.