We live in an era of "explosions". Not the least threatening of these inflationary events is the information explosion. In spite of data banks, automated indexes, and computerized retrieval systems, science is being overflooded by its products. Much of the responsibility for this state of affairs must rest with a system that tends to reward quantity rather than quality of publications, and on the resulting misap­ prehension that the aim of scientific research is the gathering of data rather than the advancement of knowledge. The sponsors of congresses and symposia who insist on a lasting record of their proceedings, the authors and editors who have no compunc­ tion about printing trivial or redundant information, and the publishing houses them­ selves, which can hardly be expected to favor restraint, also bear part of the respon­ sibility. One of the consequences of the information explosion is a change in our attitude towards new books. Whereas we used to welcome their appearance and to take them as useful and good until proven otherwise, we now greet them with suspicion and wonder even before opening them whether they were really necessary. Fortunately, some of them still are and perform a real service by taking an unwieldy mass of data dispersed in a variety of journals, and organizing it into a coherent synthesis of the state of knowledge in a given field. Such books actually serve to advance knowledge and become landmarks.