I think one of the biggest differences between book Joseph and movie Joseph are just, the sense of isolation he feels, the helplessness.
In the book, there is a scene where he is just a boy, and they run out of firewood in the dead of winter. His brother is sick, his mother far too old to even consider getting more wood herself. His father had died shortly before- and that just leaves him. He wraps up in any spare layers he can find, which aren't a lot, as his older brother is using most of them, and he gets the old ax from behind the house. He has to treck through feet of snow to try and find a tree he could manage to get, and drag as much wood as possible home for their fires. His gloves have holes in them and he almost gets lost, bc fresh snow nearly covers his tracks completely. It takes him hours, out in the freezing weather, before he has enough chopped and makes his way home. His brother is cruel to him, but he has never been more terrified of losing someone, because even if his brother is better at him than anything, he can't help but love him
His brother lives, and everything stays the same. In the movie, years later, we see Joseph in the middle of the war, snow falling down, abandoned by his leader, with holes in his gloves and half a days rations. He can't start a fire because it would only show their enemies where they were, and he is alone. He is so, so lonely and scared, but I think without the context of the book it could be written off as just the horrors of war. But Joseph has seen this before, the cruelty and loneliness and the cold. Idk idk, I think I could talk about it forever