Munro gives detailed answers to weird questions asked from readers on his website. Questions like 'If every person on Earth aimed a laser pointer at the Moon at the same time, would it change colour?' and 'How much Force power can Yoda output?' There are even some questions that Munroe shakes his head and retreats from - things like 'How many houses are burned down in the US every year? What would be the easiest way to increase the number by a significant amount (say, at least 15%)?'
The answers given are light hearted, but take the challenge seriously and with some impressive back-of-an-envelope calculation and a touch of research deliver convincing answers. There is a distinguished precedent in taking absurd suggestions (admittedly self-generated) and using them to explore the realities of science in George Gamow's classic (if now rather difficult to read) Mr Tompkins books where, for instance, he explores what would happen if the speed of light reduced to a walking pace.
The main problem with Gamow's books is that they suffer from an excess of whimsy, which was considered funny at the time, something that Munroe does occasional succumb to in his footnotes. Two other slight problems with What If are that some of the problems are so silly that it's easy to think 'So what?' and after a while the format gets a bit samey.
However, it's hard not to admire the straight faced aplomb with which Munroe deals with weird problem after weird problem - and often takes them so far over the top they become more interesting still. (For instance when asking a question about a hair dryer in a box, he considers the outcome for different powers of hair dryers up to 11 petawatts, which is considerably more than the EU likes to allow for electrical goods. (Sorry, the whimsy is catching.) )
The fact is this is a very likeable and fun book that should entertain many readers.
Review by Brian Clegg