Apparently WW2 + magic is a genre, of sorts. Bitter Seeds features a team of British warlocks going up against a squad of Nazi super-soldiers. The alt-history is pretty good, as the Nazis use their powers, especially precognition, to decisively win the Battle of Britain. British warlocks counter with a fimbulwinter, paid in a heavy blood price, and the battle escalates on both sides, with ever greater sacrifices.

Tregillis does a decent enough job with the alt-history, the points of departure, the horror and inefficiency of the Nazi war machine, and the lengths to which the Brits would be willing to go when pressed (See Operation Vegetarian). On the other hand, the mad science isn't as cool as the Cthulhu mathematics of Charles's Stross work, and the characters and writing are solid, but nothing to write home about.

Good if you're a fan of this kind of stuff and want something fun, but not really groundbreaking.