Who knew the pocket calculator was so fascinating? This was an entertaining and informative read. I found myself sharing what I learned from this book with those around me. I recommend it to fans of good and highly readable non-fiction.

Empire of the Sum will I suspect will appeal most to people who remember the 1970s and 1980s which were when the pocket calculator and its close relative, the digital watch, came from nowhere to become a must-have accessory. Their rise was meteoric, but their fall was rapid too. This book tells their story.

The need to do calculations and keep running totals is as old if not older than writing and the book covers the first technologies to help do maths. Abacus, log tables, and mechanical and desktop calculators are all introduced and explained. I learned log tables at school but never understood slide rules, though I have picked one up more than once long ago. I finally understood how they worked thanks to this book! I loved all the photos in the book, there are some brilliant ones of early devices and machines you will almost certainly never have seen, not least because many of them cost a fortune when they were first on sale. I don't think there was a single photo in this book I didn't spend quite a while looking at.

As computing power increased, the calculator became smaller and less expensive. Vacuum tubes, semiconductors, the CPU and human ingenuity eventually produced a machine that every schoolchild and office worker who needed one could afford. There were lots of people and companies working on the problem and many different products and firms knocked one another off their perches. In that way, it is very different to the mobile phone or PC which were dominated for long periods (and still are) by firms like Apple and Microsoft. But there are names you will still recognise like HP and Casio.

Everyone will reach the point in the book at which their own story begins. For me, it was the early 1980s when digital watches were the must-have accessory at school. I got a 38-step programmable calculator on which I wrote my very first "computer program". It was my pride and joy until I got an actual computer not long afterwards. In reality calculators and watches existed for many years before I was aware of them (I now realise), they were just way beyond the price range of standard households.

Eventually, the computer and then the mobile phone became general-purpose tools powerful enough not to need a separate device to do calculations and the spreadsheet/app saw off the calculator along with similar things that we all used to carry around like cameras, music players and torches. And then newspapers, magazines and books.

Empire is a good book which looks at a neglected area in our recent history. The mobile phone and the computer/tablet were the eventual winners of the gadget race, but the pocket calculator had its day and it still lives on in the classroom. I used both the Windows calculator and a mobile phone calculator app in the last week. As the book points out in its final pages, it lives on in software.