I've heard this book called "extremely long and in incredibly boring" and while I get where that sentiment is coming from, I had a positive experience with the book. The story follows Oskar Schell, a nine-year old boy who lost his father on 9/11, and his search across New York City for the lock that will be opened by the key his father left hidden in a vase.
Though Oskar is clearly the focus of the story, the narrative occasionally diverts to peripheral stories that while interesting in the conception, are frivolous and add very little understanding of the plot. Foer falls into the common trap of modern novelists of spending too much time wandering in the third quarter of the book (see the last Harry Potter for a prime example). The text, while consistently articulate, is repetitive, lacking substance, and, content-wise, boring. The ending ties all this fluff together nicely, as endings often do, but given its perhaps unsatisfying nature (to Oskar at least), it leaves open many questions as to the stylistic choices the author made. Given that Oskar is the narrator for his portions of the story, and that he is writing it after the fact, why does the ending jump out as if unexpected? Why is so much time devoted to side stories that are uninteresting (and frankly depressing) on their own, contribute nothing to the main narrative, and do not in any way advance the story to its conclusion.
I also have some questions as to Foer's authenticity. His book clearly revisits Gunter Grass's The Tin Drum and borrows the (identically named) character of Oskar to a high degree. But this 2005 book also bears striking similarity to Mark Haddon's much better 2003 book The Curious Incident of the Dog in the Night-time. So much so that I highlighted at least one occasion where the descriptive narratives Curious's Christopher and Extremely's Oskar are identical.
In short, Foer's novel is a pleasant read even if it should be a third the (already not terribly protracted) length. His use of novel's title throughout the book offers occasional bursts of energy and its double meaning gives it some needed profundity.