The Book of Doors by Gareth Brown

Cassie, a bookseller, receives a gift from her favorite customer: "The Book of Doors." This isn't just any book, it's capable of unlocking any door, anywhere in the world. Soon, Cassie and her best friend, Izzy, are stepping through portals to places previously only dreamed of. Unbeknownst to Cassie, she now holds an artifact that formidable collectors would stop at nothing to possess. And this isn't the only magical book out there, there are others that grant its owner’s unique, sometimes dangerous, powers. Join Cassie on a thrilling journey through time, and across thresholds, as she races to protect her book from falling into the wrong hands. 

This is a delightful twisty-turny magical adventure, a smartly written story that will have you utterly hooked from the first page.