This book is very good at what it does. However, you have to read the introduction to find out what it does. It is NOT a math textbook. And it is NOT a math program. You'd have to be a real geek to read it cover to cover. This is full of 1 (sometimes 2) page math things of all sorts. Little vignettes into the world of math. As such it introduces the reader to a number of things that he might not otherwise encounter. In fact, I am an engineer (lots'o'math) and I saw new and interesting things in here! Some of these are little games (answers in the back).

This book is not a "must read", but it is an enlightening read (best for high school and up). I have not read any other compilation of letters like this, so even the concept was new to me. There isn't a format, a thesis or an argument to unify the book. Rather, it is the life, work and times of Tolkien which generate the letters. He writes to his wife, his children, fans of his work, his publishers and various friends. The book is a subset of his letters (edited with the help of his son Christopher).

Tolkien has a habit of making stories that are just plain fun to read. And a sneaky little tendency to make them exceedingly rich too – offering many levels of interpretation and withstanding rigorous study by philosophers, theologians, philologists and anyone else. But all the time they remain delightful – and offer a healthy dose of poetic knowledge even to the most superficial readers. Both of these stories are 'old-fashioned' in style.

Perelandra is Venus. Ransom gets sent to Venus on a mission. Of course it takes him some time to get settled with the new surroundings again.