From the Bookshelf of Lost Without Books! (see our FB group -- sister group of The Librarianologist but focused on our members' books!)…

[close] I knew Émilie de Châtelet as one of the first female mathematicians who, after taking an interest in the work of Leibniz, published the first French translation of Newton's Principia Mathematica with commentaries and analyses that aroused the admiration of her male colleagues.
But this little book, borrowed from the municipal library, introduced me to an admirable philosopher who, after her separation from Voltaire and the experience of her 40th birthday, offers a reflection on happiness and how to achieve it, particularly for the half of humanity that are women, who did not have access to the means of men. With incredible lucidity, she wrote a very modern text that must have been revolutionary in its day. In fact, it was published after her death.
Elizabeth Badinter's preface is a very, very interesting addition to this volume.
Definitely worth a read.