One of the lines that stuck with me from Munroe's first book in this series, What If, was that when you ask physics a question, it has to answer. I really enjoyed the first book from the variety of silly and yet educational scenarios, from what happens if a pitcher can throw at the speed of light to how to use climate change to fill your backyard pool. 

I thought the questions in this book were a little more juvenile and uninteresting. What if the Solar System was made of soup? How much mass would the Earth need to lose to lose weight yourself? It was still funny but lacked the punch of the original.