This is one of those books that has almost no useful information, but you're entertained by it anyway. If you're a fan of science and hypothetical “what ifs”—not the what if’s like “what if american stop signs were blue,” but weird, crazy “what ifs” like “what if I built a jetpack out of downward-firing machine guns?” this will be an entertaining read.
The author adds a lot of character to the book with his own drawings as visual aids. Oh wait, did I mention that this is the creator of the famous XKCD comics? So, yes, you get XKCD style humor woven in as well.
This book will make you think, laugh, and wonder "who the hell asked this question?"
And if there's an awkward silence at a dinner with your in-laws, bring up one of these hypotheticals. It'll, at the very least, break the silence. However, it may get even more awkward afterward.