Philosophers from Longinus to the postmoderns have tried to answer this question. It has been defined as inherent in the object, or in the mind and reactions of the observer. It has been seen in nature, art and oratory. Some of the best philosophical minds, Kant, Burke, Hegel, and others have tried to define it. This book brings together a collection of essays that shows the breadth of the concept.
The first chapters of the book present the philosophical discussions on the subject. I was fascinated by Longinus' treatment. I'd read the Greek philosophers, but was unfamiliar with his work. The collection of essays gives a broad overview of the changing concept of the sublime giving the reader access to the entire historical perspective in one volume.
The second section of the book is a series of essays on particular aspects of the sublime ranging from religious perspectives, architecture, American understanding, Dutch literature and the fine arts. Each author brings a slightly different perspective. I found each one fascinating, but my favorite was architecture. I found the following story very descriptive of the idea of the sublime experience. Boulee wanted to place Newton's sarcophagus at the bottom of a dome pricked with holes so the light could shine through like twinkling stars. Thus the viewer could experience the quintessential sublime scene in the presence of Newton's body. This story relates the concept of the sublime to infinity and the intense feeling produced by being in the present of the sublime.
For anyone interested in the concept of the sublime, this is an excellent book because it presents so many diverse philosophical and practical discussions. It's very readable. Each chapter in addition to the philosophical perspectives presents illustrations of the sublime. I particularly enjoyed the concrete discussions relating the concept to art, architecture and nature. It's an excellent choice for both specialists and for readers simply interested in the concept. I highly recommend it.