The Discovery of Dynamics by Julian Barbour explains Kepler's work on Mars with enough technical detail and historical context that it made me think: holy crap,

The Discovery of Dynamics by Julian Barbour explains Kepler's work on Mars with enough technical detail and historical context that it made me think: holy crap, Kepler was a genius, or very lucky in some of his inspirations, like the guess that led to the equal-area law (it was meant at first to be an easier-to-compute approximation to another idea); along with the mathematical talent he worked really hard and earned that luck; and nobody else seemed to be thinking about the problems in the same way leading to Kepler's laws. I'd guess they'd have taken decades more without him, and appeared in stages. Of course his work was not done in a vacuum.