SOURCE: "Quantum Gravitationists," in Science, Vol. 272, June 7, 1996, p. 1445.

In the following review, Wald remarks that although The Nature of Space and Time may be "too technical for a layperson," most readers "should be able to enjoy the flavor of much of the discussion."

The theory of general relativity was formulated in a mathematically complete form 80 years ago, and the basic principles of quantum theory were laid out about 70 years ago. Nevertheless, only within the past few decades have major efforts been under way to merge these theories into a mathematically consistent and complete quantum theory of gravitation. Despite these efforts, research in quantum gravity remains highly speculative, with very few solidly established results and with wide disagreements among researchers not only about the best approach to take but even about what unresolved issues deserve the most attention.

Stephen Hawking and Roger Penrose are, without question, the leading developers...