So the swerve referred to in the title is a key element in the philosophy of Epicurus, and it is the unexplained motion Epicurus (a younger contemporary of Alexander the Great) needed to add to his belief in a rational universe in which atoms follow nature's laws in order to allow for, among other things, free will.
"The Swerve," on the other hand, is a mess of a book in which Stephen Greenblatt kept swerving in different directions hoping to find a topic that would justify 262 pages. Unfortunately, the thesis that drives the book could be covered pretty completely in a few thousand words -- and that thesis is that Epicurean philosophy was an integral part of the development of Renaissance thought and the modern world, and it was only luck that allowed it to survive the long centuries unscathed.
Fine as far as it goes, but it doesn't go very far, so Greenblatt then had to write a whole lot about one Poggio Bracciolini, a 15th century Roman bureaucrat who, like many of his peers, had a passion for antiquities. While out of favor, he discovered a copy of "On the Nature of Things," a summation of Epicurean philosophy written by a man named Lucretius -- and Greenblatt wants to claim that discovery was a pivotal moment in the development of the Western mind. And perhaps it was, but that still doesn't justify the 262 pages Greenblatt spends flailing away searching for a topic.
Sometimes, "The Swerve" is a biography of Bracciolini (after fathering 14 children with his mistress, he then, at age 56, married an 18-year-old and had five more children). Other times, the book discusses why and how monasteries copied ancient Greek books, and then are brief forays into the lives of other historical figures, such as Giordano Bruno.
Again, all well and good, but hardly the stuff of a cohesive work, and barely worth reading. It only gets two stars because I've always liked the philosophy of Epicurus, and Greenblatt is a competent writer. "The Swerve," however, is simply not a very good book.