The Algorithmic Beauty of Plants (1990)
This is one of the trio of great books that Springer Verlag produced around the same time. The other two are The Science of Fractal Images and Beauty of Fractals.https://www.springer.com/gp/book/9781461283492https://www.springer.com/gp/book/9783540158516Two other books that I think are good (but which are for general audiences) are AK Dewdney's Magic Machine which has a chapter about L Systems: https://www.amazon.com/Magic-Machine-Handbook-Computer-Sorce...And Computers, Pattern, Chaos, and Beauty by Clifford Pickover: https://www.amazon.com/Computers-Pattern-Beauty-Clifford-Pic...