Fun premise, though whenever I listen to sci-fi that involves multiple universes/timelines I kind of have to "blur my brain" so I don't get super lost trying to make sense of the science. That said, Crouch does a good job taking crazy concepts and making them grasp-able for regular people. This book was fun - but got a bit slow/repetitive (as one might expect with the topic is recursion) in the final 25%. There were also so plot holes that I'll omit for fear of spoilers... and I wasn't sure if they were intentional, if I had simply missed a key detail somewhere, or if they were the bi-product of dealing with a messy topic. In any case, they stood in the way of this book seaming itself up perfectly and feeling like a magic trick.