"The scientific potential of -ray astronomy has long been recognized from a theoretical standpoint by investigators in the fields of cosmic-ray research and high-energy astrophysics. Gamma-ray studies can help answer questions concerning the nature and origin of cosmic rays, both galactic and extragalactic: the nature of supernovae, pulsars, and powerful radio sources; the extent and importance of antimatter in the universe; and the nature of the universe in the distant past. The advent of satellite-borne -ray telescopes has recently made -ray astronomy a reality. The first observations, as discussed in this book, have already provided important information on galactic and extragalactic cosmic rays and interstellar gas. These observations may also have great cosmological significance. The second generation of -ray telescopes is already in the development stage. It therefore seems most appropriate at this time for a comprehensive theoretical monograph."--p. iii.