More like Time Wars

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The Apocalypse TrollNovel
David Weberstandalone novel1999
Alien invasion, about aliens, set in contemporary.
The Proteus OperationNovel
James P. Hoganstandalone novel1985
Set in mid 20th century.
FootfallNovel
Larry Niven & Jerry Pournellestandalone novel1985
Alien invasion and first contact, about aliens, set in contemporary.
“When aliens travel to Earth from Alpha Centauri, differences between alien and human psychology result in an unprovoked invasion, and the resulting resistance results in the aliens' use of a devastating weapon.”
from the catalogue
The Lost RegimentSeries
series9 books1990
Military science fiction, about survival, set in secondary world.
“William R. Forstchen's Lost Regiment series begins with Rally Cry, in which a Civil War Union regiment is swept onto a distant world where humans transplanted from many eras and cultures are farmed as food by an alien race.”
from the catalogue
Start with Rally Cry →
The Kraken WakesNovel
John Wyndhamstandalone novel1953
Alien invasion, about aliens and survival, set in mid 20th century.
“Earth's life is disrupted by the attacks of extraterrestrials whose war machines, emerging from the depths of the oceans, seem indestructible.”
from the catalogue
A Century of ProgressNovel
Fred Saberhagenstandalone novel1983
Set in early 20th century and north america.
“For centuries two meg-powers from the future have been waging war for control of timelines of history.”
from the catalogue