Haven’t read it. Keep meaning to.
Vonnegut was there; he was a sergeant in the Army who had been captured at the Battle of the Bulge.
The book got its title from the rows of stone buildings that had served as slaughterhouses before the war but were used as barracks for captured prisoners; Vonnegut had been held in house number five.
The movie is an excellent adaptation of the book and well worth seeing. But I would suggest reading the book first.
Vonnegut is definitely against the bombing and based on his experience, who would argue against him?
And so it goes.