A thoughtful book review does not need to sound like an academic essay. It should help another reader understand what the book offers and explain how it worked for you.
Begin with a spoiler-free impression. Mention the genre, tone and the elements that stood out. You might discuss character development, pacing, worldbuilding, dialogue or the emotional arc of the story.
Be specific. Instead of saying that the romance was good, explain what made the relationship convincing. Instead of calling the world confusing, identify whether the setting introduced too many names or left important rules unclear.
It is fine to discuss what did not work for you, but distinguish personal preference from a clear problem. A reader who dislikes slow burn may not be the right audience for a book built around gradual romantic tension.
If you received an advance copy or another benefit in exchange for a review, disclose that relationship. Honest, detailed reviews are more useful than ratings alone.