Red Hart Magic: The Magic Books #6

When his father marries her mother, Chris Fitton and Nan Mallory--both twelve--are thrust into a new life. While their parents are enjoying an extended honeymoon, Chris and Nan must live with Aunt Elizabeth, attend new schools, and worst of all, be civil to one another. They're certain that their future is bleak--until Chris's visit to the Salvation Army store. It is there that he finds the model of the Red Hart Inn, a structure that holds a strange allure for them both.
 
That night, Chris and Nan find themselves in the same dream--living inside the Red Hart Inn in seventeenth century England. And when danger threatens, they must set aside their differences and find a way to work together--before it's too late….

ANDRE NORTON, named a Grand Master by the Science Fiction Writers of America and awarded a Life Achievement World Fantasy Award, was the author of more than one hundred novels of science fiction and fantasy adventure. Beloved by legions of readers the world over, she thrilled generations with such series as Beast Master, Time Traders, The Solar Queen, Witch World and others. She passed away in March 2005.