Thus Spoke Zarathustra Just from the précis via Haymarket Books:
"In a work widely regarded as the most important contribution to Nietzschean studies in recent decades, Domenico Losurdo instead pursues a less reductive strategy. Taking literally the ruthless implications of Nietzsche's anti-democratic thinking—his celebration of slavery, of war and colonial expansion, and eugenics—he nevertheless refuses to treat these from the perspective of the mid-twentieth century. In doing so, he restores Nietzsche's works to their complex nineteenth-century context, and presents a more compelling account of the importance of Nietzsche as philosopher than can be expected from his many contemporary apologists."
The book is over 1000 pages, quite meticulous and the arguments powerfully stated; looking beyond Nietzsche's philosophical texts towards his letters and other written material. The book changed my outlook on Nietzsche. Even if you will not fundamentally agree with Losurdo (who does not claim that Nietzsche should be discarded, by any means), I think there is a lot to grapple with. Highly recommend.