In addition to what Slh said above, keep in mind that controller types (current mode, voltage mode, etc) are independent of the power circuit topology (buck, boost, flyback, DAB, etc). If you want to understand the control side of things, best to start out looking at it in very general terms, like a set of black box transfer functions instead of actual circuits.
Reading datasheets for PWM controller chips is also a good way to learn, I got my start reading Linear Tech white papers.