Where can I learn Switched Mode Power Supply Design?

Recently I've had terrible luck buying those little DC-DC boards from China off of eBay. We've been trying to build projects where we have some sort of wobbly input DC off of a car or solar, batteries and things. So I've started trying to learn how to design and build my own DC-DC SMPS circuits. I'm very new at this, so I'm looking for something that I can use as a calculator (input Vin and Vout, etc) but also I need to understand what's I'm doing and what's going on.