Yes,it is but Rajkumar Hirani(Director) slightly changed some few episodes according to audience satisfaction.He made the film with pure emotions that every collage student can connect to the character’s in the film .So the movie awarded as National Film Award for Best Popular Film in 2010.

Similarities:

1. Broadly speaking, the plot of the film is the same as the book. Both stories are about three students of an engineering college who form an inseparable friendship over incidents that take place in the college.
2. The three characters in the book are very similar to those of the movie. While one of them – Ryan (Aamir as Rancho) – is radical and thinks differently from the rest, the second one – Hari (Madhavan as Farhaan) – is a confused character. The book’s third character – Alok (Sharman as Raju) – is facing severe financial and domestic pressures.
3. The narrators are same in both the cases.
4. Some dialogues in the movie — “the examiner looked at me as if I had asked for his kidneys” and “define machine” — seem to be a straight lift from the book.
5. In the book, Neha (Kareena as Pia) tells her dad Cherian (Professor Viru played by Boman Irani) why her brother committed suicide due to the latter’s demanding and dominating behaviour. Similar episode takes place in the film as well. However, the book talks about this incident in much more detail than the movie which covers this branch of the storyline in a single scene.

Differences:

1. Though the narrators are the same, the narrator of the book – Hari – romances the professor’s daughter, the filmmakers give the romantic mileage to Rancho.
2. The paper stealing episode is the turning point of the book. It causes Alok to jump out of the window to commit suicide. This scene however, is twisted in the movie as Raju jumps out of the window because Boman decides to rusticate him because of hooliganism.
3. The biggest difference comes in the second half of the movie. While the book finishes at graduation, the film goes beyond it and builds on the future of the characters till 10 years later. It talks about how their careers have shaped and how their mediocrity in college played into the future.