To write a good essay about a book, you must read it not "diagonally," as many people do, but thoughtfully. It is better to return to some pages.
You can even use bookmarks on the most important places. It is good to make notes in a special notebook when reading.
You'll probably have some questions you'll want to raise in your essay, or emotions you'll want to share.
Make as detailed an outline of your future essay as possible. Remember, everything you write should play on revealing the theme set forth in the title. If it poses a question, the essay is the answer. If a claim is stated, your job is to prove or disprove it. Don't write lengthy texts about the book in general. Try to disclose as fully as possible exactly the given topic. This disclosure and should be devoted to all points of your plan.