Many authors will tell you anything! They don't even mind "I liked this book", the review is what matters.
Some will say it needs to be a 5 paragraph essay about the book, how it made you feel, and if you liked it or not.
It's all up to you! Did you like it? Did it make you laugh/cry/scream ..... Reviews can be anything to help the next reader want to read the book (or not I guess depending).
What's your take on what should be in a review?