This was just a fascinating read. It is rare to find a book where the characters, their interactions, responses, and motivations are all so simply and rightly done. There really wasn't a point where this didn't seem to work, and no point where I was just over it.
This is the story of Jacob (properly, and inexplicably, Jacobus) and his friends Connor, Moses, Gordon, and Jemma (and sometimes Hartun) as they experience and (mostly) unwillingly explore the multiverse in and around Chicago. The setup is simple - Jacob has a rough home life, is bullied at school, and has a case of Crush On 'Unattainable Girl', 1 of. As an aside, that is the second book with this in a row, and it feels old. Not the authors faults, I picked them, but still...maybe YA/NA needs to retire this one a bit. Anyway, Connor leads Jacob into an abandoned house to check it out, and they find the oversized mad scientist switch you see on the cover. Working together (as there is substantial resistance), they pull. And reality shifts.
Without telling too much, this causes major impacts on the kids. Life as they knew it is radically different - in almost all respects. This leads Jacob to return, and try again. And again, and again. Always hoping the next switch would be the switch home... Ok, it isn't Quantum Leap. The Switch does, however, owe a lot to that show - because there is the hope they will get home, and there is the Sam Beckett 'inhabit the body' aspect as well. People undergo slight physical changes on switching - nothing drastic, they are still themselves. But minor differences.
The biggest differences are in the worlds themselves, and this is where it shines The authors use a simple thing - Orange Julius - to show the seemingly minor differences in the worlds. And once that is understood, it allows greater changes.
One of my personal interests is the how of things - and that is where the book falls short. We know a lot of the surface how, but little of the different worlds is explored. The most jarring shift has, oddly, the lease fulfilling explanation. And since some of the less drastic worlds have none, that is indeed saying something. But then, when the difference is somewhat less major than the ending of Back to the Future, exposition isn't really needed. But when you give the reader a major change - and not just in who people are, but in the entire world - you might want someone to give something more than was provided.
And when that is the biggest flaw...yes, this is a good book.