Well, if you need to write a "critical book review" it means you need to provide a short piece of literary criticism about The Village by the Sea. This simply means you need to make a decision on whether The Village by the Sea is "good" or "bad" (or anywhere in between) based on the literary elements within it (such as plot, character, setting, etc.). Let's take a look at the story, and then maybe you can write your review with ease.
The Village by the Sea is a young adult novel about a poor family in the small village (by the sea) named Thul. The two main characters are Hari and Lila: the two oldest children of the family of six. With a sick mom and a drunk dad, the family lives in poverty. It is Lila who, as the oldest girl, is the mother-figure of the family. As a result, she is mature beyond her years. On the other hand, Hari helps the family by going into the city of Mumbai to find work. Life goes on, no matter what.
The wheel turns and turns and turns: it never stops and stands still.
At this point, the family's life gets a bit better. The mother gets treatment for her sickness. The DeSilvas begin helping the family financially. Hari is able to save some money from working in a restaurant while he learns how to repair watches on the side. When Hari returns from the city, the family plans to start a business with Hari's new skills. It is a positive ending with life looking more positive, and all because of Lila's and Hari's ingenuity and courage.
In regards to writing a critical book review, remember that there is a reason why this book is taught in classrooms. It must have some kind of value. Your job, as both a reader and a writer, is to figure out the value and then prove it. I would suggest that the characterization of both Lila and Hari (as mentioned in its entirety above) is a very good literary element to mention as having high value in this young adult novel. Further, the plot of the story is fairly straight forward: the exposition is when we learn about the family, the inciting incident is Hari entering Mumbai, the rising action is all of the events happening to the two main characters, the climax is Hari's realization that he can turn his watch skills into a business, and the resolution is the family coming together to start that business.
Thus, it is pretty safe to say that this is a young adult novel of value. Further, we can touch on the importance of multiculturalism here. Learning about the city of Mumbai in the context of the story is good for any child growing up in a first world nation.