I always hate how electronics and electrical engineering books organize the chapters. They never focus on the big picture, only components and how they work, but never give you an explanation of why the hell you are using them.

No one starts a circuit to just play with a bunch of resistors, capacitors, diodes, and transistors. They want the circuit to DO something, or interact with another bit of existing circuitry. The circuit you are building is often just a puzzle of how you are going to supply power at the right voltage, amperage, frequency, etc.