This is a fascinating read: Guyau, at the age of 19, wrote a 1300 page critique of Utilitarianism as an entry to a competition. The dissertation was very well received at the time; subsequently it was revised into two volumes, of which this is the first. This volume (240 pages or so) is dedicated to Epicurean philosophy.
This volume is divided into four books:
Book 1: The Pleasures of the Flesh
Book 2: The Pleasures of the Soul
Book 3: Private and Public Virtues
Book 4: The Modern Successors of Epicurus
Apparently the second volume deals with utilitarianism.... However, Guyau considers Epicurus to have been the first utilitarian philosopher. I've just finished Book 1, but already I think that this would be a great book for more people here to read and discuss. Not so much for utilitarianism, but because it's an excellent treatment of Epicurean philosophy. By virtue of being originally written in French, it has a slightly different linguistic approach to ours which will potentially depth to our understanding.