A fine historical fantasy novel, somewhat loosely plotted, but since the principal protagonists Dr. John Dee and Rabbi Loew's lives are principally those of scholars the adventure elements sometimes seem a bit forced - not really alternative history in terms of differences from published outcomes but sort of wainscoting fantasy - things that didn't get published - I liked it well enough, although none of her subsequent books have seemed to have the punch of her 1st 2 novels - The Red Magician and The Dream Years, but that may just be my changing perspective with age.