Great book -- read it when I was a teenager -- but one thing that I think makes the book a bit harder to explain to smaller kids these days is the use of relays for explaining lots of things. Its a great concept to explain things but it does tend to cause a bit of confusing for younger kids who may not have played with electromagnets as much as kids from 20-30 years ago. Not sure what to replace relays with but maybe having kids watch a super easy to understand video about how relays work would help make the book easier to understand for say like an 8 year old reading the book.
Hydraulic relays? I vaguely remember coming across a similar "bottom-up" book about how computers work many decades ago (near the end of the mainframe/minicomputer era) which used water flowing through pipes and valves as its analogy. Unfortunately the title wasn't so memorable, but I do recall the cover was a photo of a little girl filling a bucket from a spigot on the outside of a house. Does anyone know what book that was? I've searched a bit before, but had no luck.
But that would introduce more complexity (polarity, biasing, etc) that would distract from the initial purpose. With a relay they should only learn how connecting a battery to pins 1 and 2 closes the contacts on 3 and 4. Using relays with more throws they can also learn the basics of logic gates, flip flops, etc.
I believe that relays still have a place for educational purposes.
