The correspondence between Elisabeth of Bohemia (princess of the Palatinate) and Rene Descartes (famous philosopher) is worth reading, at least in parts, for any student of modern philosophy. It presents an incisive critique of Descartes' unity of mind and body, a response giving a unique insight into Descartes' metaphysics, a further critique, and then breaks off! (We are left to wonder how or when the conversation continued.) The rest is very interesting to read, but deals with less sharp areas of philosophy.

Shapiro's monograph on the correspondence is well written and provides good context. In scholarly fashion she declines speculating on the gaps in the story, but one wishes she would anyways. The summary of her (no longer extant) correspondence with Malebranche could have been translated as well. It's fortunate that these letters have, if only in some places, wormed their way into the early modern canon. Recommended reading: the Meditations on First Philosophy, since this is her response to it.