Battle of the Beasts (House of Secrets, #2)

Since the siblings' last adventure, life in the Walker household is much improved—the family is rich and the Wind Witch is banished. But no Walker will be safe until she is found, and summoning her to San Francisco brings all the danger that comes with her and puts the Walkers in the crosshairs of a mysterious journey through Denver Kristoff's books. As the Walkers travel from ancient Rome to World War II to Tibet, they'll be tested in ways that cut deeper than before, by Denver Kristoff, the Wind Witch, and each other.