Recently read:

Slaughterhouse-five or The Children’s Crusade by Kurt Vonnegut.

Another classic. Highly recommended.

The time-traveling protagonist is a WWII nobody, witness the horrible destruction on Dresden. Aliens and of course Kilgore Trout is there, who is writing away his sci-fis which no one seems to read.

Vonnegut calls the Bombing of the Dresden is the worst and had the casualties more than Hiroshima or Nagasaki. He also compares the fire bombing of Tokyo

From Wikipedia:

Kurt Vonnegut was a combat infantryman in the US 106th Infantry Division. He was captured during the Battle of the Bulge and sent to an underground POW camp in Dresden, where he witnessed the bombing and cleanup efforts first-hand. His novel Slaughterhouse-Five (1969) is based on his experiences.