Charles Platt’s Make: Electronics (and its follow-ups) was a foundational book for me, not just for learning electronics but also learning how to build practical devices in the real world.
The blue LED on the left is Project #14 and slowly pulses like a MacBook using just a few passive components.
The box on the right is Project #15 and is an intruder alarm system that sounds a noisy siren if a door or window is opened using just 555 timers.