On the back cover, this book notes that the New York Times Book Review called this book "Nothing less than a major contribution to the scientific culture of this world." That quote was, and remains, true.
Some of the Soviet Union's most famous and accomplished mathematicians wrote complex, nuanced introductions of major areas of mathematical science from mathematical foundations, analysis, geometry (Euclidian and non-Euclidian), ordinary and partial differential equations, computation, algebra, and probability. Much of it is dated, but that age sometimes works to one's advantage to be able to see the development and progression of the mathematical sciences to the modern era. Thoroughly worth the two months I spent working and annotating through the book, and I'm sure another read will show me the parts I didn't grasp the first read through. All of it is shockingly readable, builds from foundations to application, and is an excellent place for beginners or intermediate mathematicians to get a more comprehensive view of the field in general.