Given the essential facts, the writing of a textbook for undergraduates in any of the basic sciences is relativtly easy. A wealth of detail is expected; the author can let himself go. Furthermore, a provable fact in a basic science can be expected to stay provable for at least ten years and ten years is the life expectancy of the best of texts.
For a variety of reasons, however, the writing of a textbook on an advanced specialty is a very different affair. The author must remind himself now and then that the student's grasp of the intricacies of the specialty are in the nature of things necessarily tenuous, and thus he must keep rein on his own steadily advancing knowledge. But if the book is to be read by the student today, and, more important, is to be re-read by the house officer or general practitioner he will