The lure of sequels evidently proved too great for Turtledove to resist (the Worldwar series, most recently Worldwar: Striking the Balance, 1996). Accordingly, here's the first installment of a second series of alien-invasion/alternate-world yams, from a writer who's made his reputation devising histories as they weren't. The premise is that lizardlike aliens attacked Earth during WWII. Humanity, stubbornly refusing to unite against the common foe, fought the rather dim-witted Race to a standstill: the aliens, an old, conservative folk, had sent out probes more than a thousand years ago, and so were expecting no better opposition than mounted swordsmen. But now their colonization fleet is arriving, bringing with it a whole slew of new problems--for both sides. Will appeal to fans of the previous books, and--what with Turtledove's patient recaps and reminders--newcomers won't feel excluded either.