What If? Serious Scientific Answers to Absurd Hypothetical Questions

This book is the ur-nerd tome. There is no pretending: you either are the sort of person who is mathy enough, physics and astronomy-obsessed enough and all around nerdy enough to find this fun...or you aren't.

To give an example, most days, because I'm busy being a doctor, I spend a lot of time pretending that I'm not a nerd. But recently, I joined a lab where my boss is about as nerdy as I am. So comparing weekend notes, he says: I spent the weekend solving a Rubik's cross. And I said: I spent the weekend reading the new What If XKCD book. I won that competition.

To be honest, I'm not particularly motivated to write much of a review: if you're that nerdy of a person, you've read the webpage version of what-if xkcd and understand the joy that is Fermi Problems (and probably the annoyance that happens after you do a Fermi problem and you spend the rest of the day unable to stop doing Fermi problems), absurd questions about nuclear physics, random statistics and clever stick-figure illustrations.

The key points are these: I religiously read What If XKCD every week, and have read every single one published on the web. The book still had plenty of new things that I had never seen before. There are some extras in the book: one line answers to particularly weird questions. I was anticipating a major drawback of the book to be the loss of hover text and footnotes that appear in the online version; this is replaced by captions and the old-school form of footnotes (i.e. footnotes). However, this is not a great book to read far apart from the internet: it's impossible to get through the whole thing without having strong compulsions to google side questions.

P.S. The worst part of this book is in the acknowledgements when he says he already has an expert on genetics. Note to self: scheme to take out previous genetics expert and become Randall Munroe's personal brilliant geneticist...

Anyone who is familiar with Internet culture has either heard of xkcd, or either encountered one of the webtoon's inimitable comics. Randall Munroe's famous style has spawned a huge variety of comics on science, technology and philosophy, and has helped to make daily webcomics great again.
Right from its inception, xkcd and Munroe were asked to answer a variety of hypothetical scenarios by its readers - ranging from the curious (‘What would happen if a bullet as dense as a neutron star was fired into the Earth?') to the slightly macabre (‘What if the Earth was made entirely of protons and the moon entirely of electrons?'). Munroe started answering these absurd questions with a ton of Math and physics - that is, to say, seriously. The series of QnA was spun-off into a separate section of the site and was termed ‘What If' - this book is simply the entire section in print form, plus previously unseen questions.
Not everything in the book is about anarchy and destruction though - that is reserved for the second half of the book. The first half of the book is comprised of innocuous questions, mostly relating to lightning, time travel, and astronomy.
Even if you're not interested in computation and weird thought experiments, this book is a must-read, if only as a testimony to human imagination. Mind-blowing doesn't even begin to cover it. This is a work of art, and deserves to have space on every bookshelf.

This book is awesome. Randall Munroe does a really good job with explaining science to everyone (everyone who knows xkcd already knows this).

The topics are short but informative. You always get way more information than you thought, and with its on point humor it's just fun to read.

I really learned some new stuff, and even though most of the topics are really crazy, I already could shine with some knowledge or facts around my friends.

I really can recommend this to everyone. Fun!