I’ve been enjoying James Essinger’s very readable ‘A Female Genius’ (http://www.amazon.co.uk/Female-Genius-Lovelace-Daughter-Computer/dp/1908096667) - a biography of Ada Lovelace in which he examines all her letters including those to Charles Babbage. He comes to the conclusion that her vision was more far-reaching and insightful than Babbage’s and that, had he had the grace to recognise this, the history of computing might have been different.
The Lovelace-Babbage collaboration is only a small part of the book which is more concerned with describing the context in which Ada Lovelace managed to get as far as she did in a society which believed that mathematical study might damage female brains.
