The problem with Diary of a Young Girl
is that it's the diary of a young girl, and young girls, as you may remember from when you were one, or spent all your time trying to make out with one, are awful. It's like 300 pages straight of "No one understands
I suppose the reason this made it on to so many high school curricula is that young people might relate to it, and I suppose some of them did - but there's nothing in this to make it any better than any other diary of a young girl. It doesn't depict the horrors of the Holocaust. It depicts the boredom of being locked in an attic for two years.
Thumbs up for the hot girl on girl action (which you may have missed if you didn't read the unexpurgated version - I'm not kidding about this, Anne Frank totally made out with a chick), but in the pantheon of literature about being locked in an attic, [b:Flowers in the Attic|43448|Flowers in the Attic (Dollanganger, #1)|V.C. Andrews|http://d.gr-assets.com/books/1327880853s/43448.jpg|3311885] is still the gold standard.