Piers Anthony's
Out of Phaze Book Four of the Apprentice Adept Series
Welcome to the astonishing parallel worlds of Phaze and Proton. Where magic and science maintain an uneasy truce. Where an accidental mind-switch plunges an...
A dissident faction of the Clan, the alternate universe group of families that has traded covertly with our world for a century or more, have carried nuclear devices between the worlds and exploded them in Washington, DC, killing the President of...