This movie is nothing like the book...

Thank you for sharing. I hope your thread will encourage others to respond. I'd like to know the differences.

To be fair though, the book is not really adaptable to movie.
If you a book that is so full of interesting narrative and metatextual shenanigans, there is no way to really adequately translate that into a visual medium.
That being said, they really shouldn't have changed Oscar the way they did.
In the book he came across as a smart and genuinely nice boy who is simply traumatized and overwhelmed and lashes out occasionally because he has no real way of dealing with his situation. That seemed totally plausible to me. Movie Oskar was already a jerk before 9/11 as we could see in the flashbacks and just got (only slightly) worse afterwards.
He was changed from a traumatized, highly intelligent and well fleshed-out boy to a stereotypical and rather flat asperger-patient (in the sense that his -in the novel not mentioned - Asperger really defined him in the movie). Trauma and loss was the whole point of the novel. 9/11 just served as an example. Foer explicitly rejected the "9/11 was a singular and unprecedented event" - narrative. Which was exemplified by bringing an account of a Hiroshima-Survivor and the life stories of the grandparents (Dresden-bombings survivors) into the mix and showing that Oskar is not singular in his experiences and his helplessness since even his grandparents are burdened by the same guilt, fear and anxiety and spent all of their lives to just survive and find meaning in a meaningless world.
The point of the movie, it seemed to me, was to produce a cheap tearjerker to milk the american public's shaken sense of self-esteem after 9/11 by showing the melodramatic journey of a weird kid through 9/11 New York.
The book had that journey (although with a severly less weird kid) too, but it had so much more.

And why do we need to see the renter in the beginning of the movie? I really liked that he was played as an imaginary friend of the grandmother in the movie.

But what I did like was the Abby Black-Scene. It made so much more sense in the movie. But that could be because the reader experiences it through Oskar's eyes, who probably does not understand that there is a divorce going on and does not pay attention to or comment it much. When I read this scene, I thought that Mrs. Black maybe could be a prostitute and the screaming man could be her John. It only got cleared up much later when Oskar speaks to Mrs. Blacks husband.

If in the book the boy doesn't find his dad, who is actually renting house at that circled address with another family (in cohorts with good old granny and gramps, who is actually a nazi war criminal in hiding, and had his tongue cut out by Dr.Mengele for failed attempt at surrendering to the allies, whom he is useful to because of his heavy water research and fuel-oxidiser ratios knowledge he got during an Ahnenerbe seance), and decided to fake his '9/11 death' to 'cushion the blow' (pardon the pun) - then i'm not reading it.
Thank you