4.5 stars. 
 Time travel is a tricky subject to write about, and this book is easily my new favorite in the genre. Strong characters, an interesting storyline, and an incredible variety of settings in different countries around the world and different time periods throughout history. My only complaint is that it felt a little slow to start, but the fast pace of the rest of the book more than made up for that. 
 Can't wait for the next one in the series!