Far from it: Black Book takes seriously the idea that just because there was a war and a genocide going on, people didn't necessarily stop falling in love or having sex, or that those things didn't often matter just as much as other life-and-death situations. There are no battlefield or concentration camp scenes in this movie, but both are always ominously lurking just beyond the characters' lives, and they are keenly aware of this, even if they never explicitly say so. The entire story is motivated by the desire of heroine Rachel Stein (Carice van Houten), a Dutch Jew, to stay out of the clutches of the Nazis, and what she does she always does primarily in pursuit of that goal.
The film starts with the bombing of the farmhouse in which Rachel has been hiding, and that sets her on an odyssey through the underground resistance, where she dyes her hair blond and takes on the name Ellis de Vries to blend in with mainstream society. Not content simply to lay low until the war ends (and at the point the movie begins, Germany's loss is already imminent), Rachel/Ellis teams up with anti-Nazi fighters to take on the German occupants of Holland.
This being a Paul Verhoeven movie, that means she is soon assigned to seduce and attach herself to a senior SS officer (Sebastian Koch), something which requires her to engage in an activity that's vintage Verhoeven: making use of hair dye to ensure that the carpet matches the drapes. This and other moments (there is ample naked female flesh—and some male—on display throughout the film) make Black Book sometimes play like Nomi Malone vs. the Nazis, but that's exactly why it works so well.
Ellis may be a dedicated anti-Nazi crusader, but she isn't some noble Oskar Schindler—she's a lusty sexpot who genuinely falls in love with the Nazi on whom she's supposed to be spying, who'll flash some leg at a passing group of German soldiers even as she's on her way to meet with someone who's job it is to ensure that those same soldiers don't kill her. Verhoeven also has the audacity to portray at least one Nazi as rather sympathetic, and to show the liberators and liberated as sometimes nearly as cruel as the people they fought against.
The staid World War II epic has become Hollywood's most boring awards-baiting genre, and Black Book sidesteps all that by being unabashedly lurid and melodramatic, with tons of suspense and plenty of silly plot twists. It goes on a little too long, and some of the more insane set pieces are too over the top to take seriously, but overall it's the most entertaining movie about avoiding systematic extermination to come along in quite some time.