Appearance of a small brochure prof. G. G. Slyusarev, an outstanding optician-calculator, author of the fundamental "Theory of calculating optical systems," is quite timely. Within the framework of a small brochure, G. G. Slyusarev could explain not all the paradoxes of practical optics, and much is involuntarily set out briefly and schematically. Undoubtedly, further books and brochures explaining optical paradoxes will be required, but today we must welcome the first swallow in this necessary matter. S. Vavilov