I’ve expressed my appreciation for Nightwatch already. Daywatch (its sequel) was pretty good, but a little inconsistent. Fortunately, Twilightwatch, the third in the series, is excellent. Not as good as Nightwatch, but it’s still well worth reading Daywatch to get to Twilightwatch.
I particularly love how Sergei Lukyanenko keeps redefining good vs. evil. It’s a great series.