So, basically, it's a wooden box with a double-paned glass window on top, a reflective lid, and a black tin interior. But there is some science to its construction and operation. The angle of the glass window should be adjusted depending on the global latitude that the oven is to be used at. When using the oven, it should be facing North if you're in the Southern Hemisphere, and South if you're in the Northern Hemisphere, so it can catch as much sunlight as possible. The angle of the reflective lid should also be such that it will reflect as much light into the oven as possible. Also, only black colored cookware must be used in the oven.
Ok, that's all well and good, but the most important thing about this cheap, light, environmentally friendly device is that everything that comes out of it is DELICIOUS. It generally takes the oven 4 - 6 hours to cook something, so you can only really cook one thing per day, per oven - usually dinner. However, since the solar oven cooks so slowly and evenly, meat and fresh veggies come out tender and tasty - the kind of tender and tasty you can only get by cooking something for 6 hours. Bread and cakes don't rise as much in a solar oven, but they somehow retain more flavor. Since the physics of cooking something using solar energy is different from using fire or an electrical heating element, it is literally impossible to burn food in a solar oven. This means, you just have to pile your ingredients into a pot, set up the oven, put the pot in, then come back when everything is done. Cooking doesn't get much easier than that, and the results are really spectacular. Ron Popeil needs to start selling these in infomercials right away, because solar ovens really are a miracle appliance. Plus, how awesome is "Solar Stew" as a name for a recipe?
Of course the one disadvantage is that you need the Sun. Unfortunately, it's the rainy season right now in Kavango, so the solar oven hasn't seen as much use as I'd like. The rest of Namibia is pretty much desert, however, so I bet my fellow volunteers are getting plenty of use out of theirs. Lucky skunks.