Cover art
Saberhagen, Fred. The Mask of the Sun. Ace 1979.

Saberhagen, Fred. The Mask of the Sun
Divergence: 1536 CE
What if: The Inca rebellion against Spanish domination succeeded.
Summary: A man from our world gets involved in a time war between Inca and Aztec timelines, seeing action in old Cuzco.
Published: Ace 1979 (0441520774w88 android); and Tor 1987 (0812553098, 0812553101), 1991 (0812513576BUY).

Cover art
Saberhagen, Joan Spicci, and Robert E. Vardeman (eds.). Golden Reflections. Baen 2011.

Saberhagen, Joan Spicci, and Robert E. Vardeman (eds.). Golden Reflections
Summary: Anthology based on the time wars of Fred Saberhagen's The Mask of the Sun. Includes Saberhagen's original short novel, plus Walter Jon Williams's "The Fate Line", Daniel Abraham's "Wax, Clay, Gold", John Maddox Roberts's "The Conquistador's Hat", Harry Turtledove's "Eyewear", Jane Lindskold's "Like the Rain", Dean Wesley Smith's "Remember", and David Weber's "Washington's Rebellion". One or two of these stories may be secret history rather than alternate history.
Published: Baen 2011 (1439134154BUY, 1451637748BUY).