I have always thought it was a wonderfully delightful way to introduce children to those sort of concepts. It was more EE/CE than coding (and the rest of the book was heavily ME), but I think the approach adapts to coding equally well.
Also, libraries in general, including university libraries. Some books on homeschooling (such as Grace Llewellyn's _Teenage Liberation Handbook_) are full of pointers for self-study.
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