As Author Gary K. Wolfe notes in this book's preface, the eleven essays it contains were written over many years and without any overarching theme in mind. However, there is nevertheless a degree of unity to the book, and even apart from that issue, it's one of the most engaging books of science fiction scholarship I've read in a long while.
The general topic of the book is the issue of genre, specifically as it relates to science fiction, fantasy, and horror. A few chapters examine in some depth the ways in which many books, and more broadly, the works of many authors, defy any simple genre classification. Other chapters look within single genres or sub-genres, analyzing how different genres are defined, how divisions are formed within a genre, how related genres such as science fiction and fantasy distinguish themselves from each other, influence one another, and sometimes blend at their boundaries.
Some of the chapters I found most interesting were the following:
Chapter 2, which has the same title as the book and which is its central essay, starts with a look at how genres such as science fiction became defined and developed their "specific market identities." It then goes on to look at how writers within those genres have begun to "subvert or transform the genre expectations that largely derived from those market identities."
Chapter 6 focuses on the post-apocalypse sub-genre of science fiction and has some interesting insights, for example the fact that the "apocalypse" of such stories is almost never absolute, and indeed is often represented as a point of rebirth for humanity and civilization, thus presenting the paradox that "fictions that begin with cataclysm often include some of the most strangely luminous visions of affirmation in the whole of fantastic literature."
Similarly to chapter 2, Chapter 10 looks at "twenty-first-century stories" -- a range of recent fiction that makes use of the tropes of various fantastic genres but is not controlled by those tropes. Thus these stories may include elements that seem clearly "science fictional," and yet ultimately will diverge from the conventions and expectations of SF.
Chapter 11 presents an engaging examination of the field of science fiction scholarship itself; its history, the distinction between theory-based academic study and more reader- and fan-directed criticism and reviews, and other issues. This chapter focuses largely on SF critic and encyclopedist John Clute, and I found it both informative and fun reading.
The writing of this book is excellent, presenting interesting and sometimes complex ideas without slipping into unnecessary jargon or overly convoluted sentence structure. I highly recommend it to anyone interested in science fiction studies or genre studies in general.
Full disclosure: I received a copy of this book in return for a review.