This book is an introduction to the philosophy of Arthur Schopenhauer, written in a lively, personal style. Hannan emphasizes the peculiar inconsistencies and tensions in Schopenhauer's thought--he was torn between idealism and realism, and between denial and affirmation of the individual will. In addition to providing a useful summary of Schopenhauer's main ideas, Hannan connects Schopenhauer's thought with ongoing debates in philosophy. According to Hannan, Schopenhauer was struggling half-consciously to break altogether with Kant and transcendental idealism; the anti-Kantian features of Schopenhauer's thought possess the most lasting value. Hannan defends panpsychist metaphysics of will, comparing it with contemporary views according to which causal power is metaphysically basic. Hannan also defends Schopenhauer's ethics of compassion against Kant's ethics of pure reason, and offers friendly amendments to Schopenhauer's theories of art, music, and "salvation." She also illuminates the deep connection between Schopenhauer and the early Wittgenstein, as well as Schopenhauer's influence on existentialism and psychoanalytic thought.
Schopenhauer is an overlooked philosopher. He's not a rigorous thinker in the analytic sense, but his critiques of Kant's metaphysics and moral theory are insightful and his theory of the will is historically crucial to the development of Nietzsche and Freud. Wittgenstein is also visibly influenced by Schophenhauer, particularly in the later, more mystical-sounding propositions of the Tractatus. On top of all that, he's readable, as 19th century German philosophers go.
Hannan's book is meant as a personal perspective on Schopenhauer. She says early on in the book that she is drawn to Schopenhauer's pessimism, in particular. And she plays at the edges of psychological discussion of the roots of her own and Schophenhauer's pessimism. I think a more in-depth discussion of Schopenhauer's life, maybe dipping into Helen Zimmern's 1876 biography of Schopenhauer, would have been helpful.
As it is, it's a relatively easy-to-read introduction that does a good job of focusing on what is most influential and insightful in Schopenhauer.
"There are obvious similarities between Spinoza’s metaphysics and Schopenhauer’s. Both take the entire universe to be animate. Both take all events to follow from preceding events with necessity. Both are struck by the suffering caused by our desiring nature and the indifference of the universe to humankind. Both recommend quieting the passions as a means of salvation. Of course, Spinoza is resolutely optimistic, whereas Schopenhauer is pessimistic. The deep difference really dividing the two is that Spinoza sees the universe as rational and neither good nor bad, whereas Schopenhauer sees it as irrational and bad. Let us focus, however, on the panpsychism that Spinoza and Schopenhauer share. Such panpsychism is, in essence, the notion that all reality contains within itself a kind of drive, toward activity, toward ever greater complexity, and eventually toward consciousness." (p.56-57)