The Netflix adaption is heavily rewritten, removing and adding characters and scenes to the story, changing the ending (to the point where the title no longer has the meaning it expresses in the original), rewriting dialogues to remove contemporary context that is not relatable today and both focusing on and exploiting violent content.
There's some pretty heavy criticism in German press of the adaption, to the extent of quotes like "you have to wonder whether the movie director even read the book" or, going further, "whether he only read it to find scenes to cut so they could put their own scenes into it", alleging that 80% of the movie has nothing to do with the book beyond the character names.
In Germany the book is mandatory reading in high school in most places, typically around 11th grade.
If you ever get to read the book do so keeping in mind that it is based upon Erich Maria Remarque's own diary from a month on the frontline, heavily expanded with similar diaries of friends of his, and adapting events into a fictionalized exaggeration; he actually had to rewrite and censor it several times in order to find a publisher in 1927-1929. He also wrote a much less-known sequel in 1930-1931 ("Der Weg Zurück" - "The Road Back", there's a 1937 movie adaption as well) which mostly deals with shellshocked soldiers trying and failing to reintegrate into society.