Max Caspar's 1947 work, Kepler, is the definitive biography of the astronomer.
Although the full translation of the New Astronomy is out of print, William H. Donahue has produced an abridged edition and course module entitled Selections from Kepler's Astronomia Nova, as well as a translation of Kepler's Optics.
Kepler's Harmony of the World is available in a translation by the American Philosophical Society, and Kepler's first work, the Mysterium Cosmographicum, is available here in a 1981 translation by A.M Duncan.
The staff of NASA's Kepler Mission has encouraged us to include The Sleepwalkers, Arthur Koestler's best selling history of early astronomy, Kitty Ferguson's Tycho & Kepler, and James A. Connor's Kepler's Witch.
We also recommend the Leibniz-Clarke Correspondence and its engaging discourse on the subject of metaphysical versus mathematical principles. Clarke argues on behalf of Newton's mathematical interpretation, while Leibniz can be said to defend Kepler’s metaphysical approach.
For younger readers, we recommend Archimedes and the Door of Science.
We recommend a number of books below for a general audience on the history of science: