These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Crowning Moment of Heartwarming: ...Despite the mayhem that followed, Bruno found that he was still holding Shmuel's hand in his own and nothing in the world would have persuaded him to let go. Also a Tear Jerker.
Some Anvils Need to Be Dropped: The setup of the two boys meeting at the fence and the contrivance of Bruno being able to dig under the fence can be nit-picked for historical veracity and plausibility, but the story very effectively highlights the evil of locking up and exterminating people because of their race and/or religious background, as well as the danger of indoctrinating impressionable children about the supposed 'evils' of other groups. While the ending may not have ever happened to any SS Officer and his family in real life it does make the point that people who do evil may find their actions rebounding on them in major and unexpected ways.
Captain Obvious Aesop: Don't discriminate people based on what they're born with! ...sadly enough, the above trope still holds true in the present day.