Sadly now out of print, which is a shame as this is a utterly brilliant book, full of facts and wonderful whimsically drawn cartoon illustrations.
There are still times now when someone will mention a subject and I have a rough understand of it from this book, which I originally got when I was around eight years old. The cover is held on by sticky tape and all the page are bent and creased but it still gets dug out and read every few years.
The author Tim Hunkin has since but all the original contents on the book online for free here, but if you can find a second hand copy on ebay or in a second hand store, I highly recommend it, and any kid with a curious mind will love it.