Ray Tracing in One Weekend is a $2.99 Kindle book with an associated blog in1weekend.com where I will outline some other one weekend projects (or promote yours-- this is a fun thing to do). It is very much book for novices to get to a cool picture ASAP.
Here's the image it ends with:
And interesting aspect of that image is the glass balls seem to float because they may focus light but with a diffuse field that mostly cancels out. That was news to me and it took me a while to confirm it is no bug. Try it with a real glass sphere next time it is cloudy :)