Final answer:
The corrected sentence with proper punctuation is: "Have you read R.K. Narayan's novel 'The Guide'? You must read it."
Step-by-step explanation:
The correctly punctuated sentence would read: "Have you read R.K. Narayan's novel The Guide? You must read it." When punctuating the sentence, we add a quotation mark at the beginning and end of the title of the book to show it's a title.
Also, we use an apostrophe after Narayan to denote possession, indicating that the novel belongs to him. Additionally, a question mark is added after "The Guide" to separate the two sentences and indicate that the first part is a question.