One of the first books I downloaded onto it was Luminous Moments by the late Sir Paul Callaghan. What a cracking read.
I don't think I've ever read a book that made me cry during its introduction, which is written by Sir Paul's daughter Catherine. She describes, in painful detail, Sir Paul's fight with cancer and his characteristic scientific approach to his own illness. The rest of the book is a collection of Sir Paul's own writings, blog posts and interviews.
For his own part Sir Paul describes his childhood in W(h)anganui, the trials and tribulations of being a father, and fatherhood in general. He describes his love of science and the complexities of magnetic resonance (which I didn't really get, to be honest. But now I can now safely claim that I know where to find out about magnetic resonance!), his major field of research along with 'nuclear orientation'.
Another area of Sir Paul's work was communicating to the general public about science. One of his many projects was a documentary on transforming New Zealand's economy to a knowledge-based one where "the talented want to live" (the whole documentary is online here). The book acknowledges this work and has an entertaining interview with Kim Hill on Pseudo-science, and whether it's dangerous or not.
Sadly, Sir Paul is no longer with us - something this book can only compound as it reveals another brilliant Kiwi mind lost. Nonetheless it's still a cracking (and important) read, and a real bargain at less than $5.