There is arguably something for everyone here, which inversely means that there are probably some bits, depending on your mathematical knowledge and interests, that you will either find too trivial or too heavy going. But the format makes it easy to skip through to the next. I personally most enjoy the logic problems (though a small black mark for featuring a near-identical "moving the cups" problem to one in the third book) and, much to my surprise, the geometry, which I suppose took me back to a more innocent time. There were inevitably some entries where there was a strong feeling of 'so what?', leaving the reader suspecting that mathematicians need to get a life. And at least one where I think the answer is wrong, if you apply the same logic as applied in an earlier tricksy question. (It's the one about pigs and umbrellas, if you must know.)
Funnily, what works least well are the bits that are most like a conventional popular maths book, that describe famous mathematical problems and their context, such as the four colour problem and Fermat's last theorem. The entries for these are rather longer than the rest, but obviously much shorter than, say, Simon Singh's brilliant book on Fermat. That means that you get concentrated fact, but none of the interesting detail that makes a popular science or maths book appealing. For me these sections just don't work and I largely skipped them.
But - and that's the joy of the format - it really doesn't matter. Because in a few pages there will be something else, and something else, and something else again to entertain and tickle the brain cells. It's notable that I got not just one (about a strange set of dice) but two blog posts (the other being about an oddity in my review copy) out of this book - because it made me think, reminded me of some old favourite problems and puzzles, introduced plenty of new ones and entertained. What more can you ask from maths.
Review by Brian Clegg