The Practice Effect - David Brin

From one of the most critically acclaimed and well-loved authors of contemporary science fiction, a highly imaginative and exciting story as only David Brin can write . . .
"High spirits and inventiveness . . . Dennis's adventures, which can only be called rollicking, are legion."—Isaac Asimov's Science Fiction Magazine
Physicist Dennis Nuel was the first human to probe the strange realms called anomaly worlds—alternate universes where the laws of science were unpredictably changed. But the world Dennis discovered seemed almost like our own—with one perplexing difference. To his astonishment, he was hailed as a wizard and found himself fighting beside a beautiful woman with strange powers against a mysterious warlord as he struggled to solve the riddle of this baffling world.
"A delightful, often very witty story, with the underlying thoughtfulness we expect from David Brin."—Poul Anderson