Here are a couple of books that I enjoyed regarding geometry. You can also go through the list of accounts that I follow with my generative art Instagram account to find some cool people/art.
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Islamic Geometric Patterns - Eric Brourg
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How to Make Repeat Patterns: A Guide for Designers, Architects and Artists - Paul Jackson
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Sacred Geometry: Philosophy and Practice - Robert Lawlor
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Brilliant.org (interactive courses)
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Quanta Magazine (cool science blog)