Searchable source that brings together 30 years of Gardner's "Mathematical Games" column which ran in Scientific American from 1956 to 1986.
If you could find a collection of the Mathematical Games articles from Scientific American, those were entertaining and required little background knowledge, but conveyed the fun of math.
Geometry is a good subject because it doesn't have very many prerequisites other than basic arithmetic, and the older textbooks were mostly about proofs. (Note I'm biased, proofs are what made math come alive for me).
There was a time when they gave meaningful direction to young readers.
Albert G. Ingalls, "The Back Yard Astronomer." Martin Gardner, "Mathematical Games" C. L. Stong. "The Amateur Scientist"
After Stongs death, SciAm displayed a halfhearted attempt to keep a few back pages, but around 2000 they dumped the whole idea of citizen science.
Despite the launch of a nationwide "Maker Movement" SciAm's new management couldn't understand why anyone would care. Today, the publication has made itself irrelevant.
This generation has found a new outlet for DIY science and it is called YouTube. Maybe you should check it out. You might learn something.
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The column was continued by Douglas Hofstadter.
https://en.wikipedia.org/wiki/Martin_Gardner_bibliography#%2... - That's a list of the books (and on that page many other things) collecting Gardner's Scientific American "Mathematical Games" articles.
https://www.cambridge.org/us/academic/subjects/mathematics/s... - First 4 of the reprints available here (or a bookseller of your choice).
It's Metamagica Themas, I think - an anagram of 'Mathematical Games'; the Martin Gardner's column in Scientific American which proceeded it.
A lovely book.
Sadly, the old Amateur Scientist columns are hard to come by unless you have access to a library with Sci American going back to 1952. (The old Mathematical Games columns by the late Martin Gardner are great too. I first read about public key encryption just a few months after Rivest, Shamir and Adleman wrote the MIT memo on it because it appeared in the August 1977 column by Gardner.)