Some people have a fear of mathematics, possibly because of the abstract teaching methods that were in use in my schooldays. I get the impression that things have changed somewhat since then, but in any case this book provides an easy to understand some of the things that happen in everyday life.
The first chapter begins with numbers that occur frequently in plants, explaining why four-leafed clovers are rare. Depending on the species, plants tend to have three leaves like clovers, or five leaves like buttercups, pansies and primroses, rather than four. The chapter then describes more curiosities about numbers and ratios that occur in plants.
The ninth chapter deals with the title of the book, explaining why buses that begin their journeys at evenly spaced intervals and travelling along the same route don't usually arrive at their destination at evenly spaced intervals. The author suggests that it is quite common for a bus to catch up the one ahead, but that it is most unlikely that a third bus will catch these two, so buses may come in twos but rarely threes.
Other chapters deal with route planning, opinion polls, betting, apparent coincidences, angles, making tea, cutting cake, secret codes, sports rankings, game theory, set theory, map reading, traffic jams, queues, scheduling, logic and deduction. If some of these sound intimidating, don't worry as they are all presented in an easy-going style that makes them more interesting than they might otherwise be.
The final chapter presents a few mathematical tricks that you can play on unsuspecting children as a good way to get them interested in numbers. All in all, this book presents mathematics in an entertaining and easily accessible way. If you enjoy it, there is a sequel, How Long Is a Piece of String?
by the same author, but if you are choosing between them, I'd nominate this one as slightly the better of the two.