 ratio (SNR) available at the channel's end. The second part of Emmanuel Desurvire's book is about quantum information theory. This is where the telecom scientist, together with the author, is taken out to a work tour that she or he may not forget, hopefully a most stimulating and pleasurable one. With the notion of reversible computation and the Landauer Principle, the reader gets a first hint that "information is physical." It takes a quantum of heat kT to tamper with a single classical bit. From this point on, we begin to feel that quantum mechanics realities are standing close behind. Then come the notions of quantum bits or qubits and their logic gates to form elementary quantum circuits. Such an innocuous introduction, in fact, represents the launching pad of a rocket destined to send the reader into QIT orbit. In this adventurous journey, no spot of interest is neglected, from superdense coding, teleportation, the Deutsch-Jozsa algorithm, quantum Fourier transform and Grover's Quantum Database Search, to the mythical Shor factorization algorithm. Here, the demonstration of Shor's algorithm turns out to be very interesting and useful. Most physicists have heard about this incredible possibility, offered by quantum computing, of factorizing huge numbers within a short time, but have rarely gone into the explanatory detail. Shor's algorithm resembles the green flash: heard of by many, seen by some, but understood by few. The interest continues with a discussion of the computing times required for factorization with classical means, and to meet the various RSA challenges offered on the Internet. The conclusive chapter on cryptography is also quite original in its approach and con- clusions. First, it includes both classical and quantum cryptography concepts, according to the author's view that there is no point in addressing the second if one has not mastered the first. Cryptography, a serious matter for network security and privacy, is treated here with the very instructive and specific view of a telecom scie