This book was... underwhelming. 
 Don't get me wrong, it has a great premise. And the opening hook is brilliant. But the rest of it is generally poorly executed. The main characters had very little depth and the majority of the book is spent on the trivial and the mundane. Which has it's place, certainly, but when you pick up the book with expectations from the synopsis, it just doesn't deliver. And the tone borders on incredibly juvenile at times, which was frustrating and annoying. 
 Even the major reveal at the end was predictable. Not that it was poorly done, because it's a really neat idea and I was glad to get that confirmation, but it was... anticlimactic. Also, I'm sorry, but apparently my suspension of disbelief is broken, because while I have no problem accepting the rooms of the house will transport us to other places (view spoiler)[ I just don't buy a 15 year old facing off against a gladiator. Or a 12 year old with a machete running away from tigers. (hide spoiler)] 
 Also, I was sort of annoyed that this book, short as it is, was really just a giant set up for everything else to come in the series. Not that I wasn't aware this was a series when I started, but I expect a little more. Because it's clearly a ploy to try and keep readers interested. Which is just not working out for me.