Book reviews typically give an overview of the major events in the plot of the story, an exploration of the main characters, a word about theme, and comments on the author's writing style. Reviews might also include the reader's response to the work and some opinions on the type of audience that might appreciate the work.
So, in a review on Adiga's The White Tiger, take care to note the major events of Balram's journey--his family background, his move to become the driver for Mr. Ashok, some of the trips that Balram made in the car, the killing of the boy, Balram's murder of Mr. Ashok, and Balram's opening of the taxi company. Major characters are of course Balram, Mr. Ashok, the Mongoose, and Pinky Madam. When addressing the style, you might discuss the novel's form which is a letter to the Chinese Premier. Also, the narrative voice created for Balram is sarcastic and witty. Finally, since there is much history and discussion of socioeconomic and political issues regarding India in the novel, consider what type of audience might appreciate these topics.