An Alternate History. Near future earth temporarily 'Exchanges' pieces of itself with an alternate reality where humans never developed and the large, fierce ice age animals stills exist. More
Exchanges have become ‘routine catastrophes’, sort of like a hurricane or a major earthquake. Having their town pop into a wild, dangerous alternate dimension for two weeks is hardly routine for the people of Rockport though. One of them, Sharon Mack, has to fight her way through threatening animals, a brutal street gang, escaped convicts, and the "Church of the Second Chance" to get her daughter back.
Exchange has a rich, unique setting. It has strong, colorful, ambiguous heroes and villains. It has an intricate plot--wheels within wheels as one character puts it--that should keep you guessing until the end, as powerful ambitions clash over the future of both realities.