This is the most amazing book I've read in a long time. First, you must know and understand the definition of "magical realism". The author incorporates in his writing a mixture of fantasy within the realm of the real world. That the narrator of this book, Oskar Schell is only nine, is suitable and believable for the magical realism which is present throughout.
The book is about Oskar's coming to terms with the fact that his father, Thomas Schell, has died in the 911 attack on the Twin Towers in New York City. Oskar is the only one who heard his father's multiple calls from the tower before its collapse and his death. Oskar hides the answering machine from his mother and grandmother, and spends the book looking for the lock a key which belonged to his father accompanies. The only clue is the word "Black," so therefore, he searches the city for all the 200+ people named "Black." All of whom, are uniqe and wonderful in their own way, but also suffering from the effects of 911.
So, to answer your question, a few examples of magical realism are Oskar's imagination as he attempts to deal with the suddenly dangerous world in which he finds himself where buildings can suddenly collapse and loved ones can disappear. He pretends he can fly, he envisions his father and imagines speaking to him, his grandparents have an apartment divided into zones of "something" and "nothing" where they can submerge themselves into non-existence.
The question as you read, is: What seems to be real and what is fantasy/invention? There are many more examples than what I have given you here, and it will be easy for you to find them within the confines of Oskar's intellectual and inventive nine-year-old mind.
Look closely at Oskar's epic adventures in search of the Blacks and the answer for the key/lock. They are fun, heartbreaking, and fantastic.
Above all, enjoy reading this amazing book.