Writing Reviews

When you sit down to write a review on a book what do you like to include in your review? Do you actually do a "book report" of sorts and give a synopsis of the book or do you just give your thoughts and feelings on the book and how it was written? 

I am always mixed when it comes to this. People are already going to know what the book is about based on the description on the back of the book or inside the front cover, and they may see it in write-ups on different avenues such as Goodreads, Amazon, bookstore websites, etc. So why would I need to re-write that and possibly give away something in the book that should be left a mystery for any potential readers? Plus, don't you feel like you are back in school and doing a book report when you do that? 

For me, honestly, I tend to do both. I don't really like to give a synopsis in my reviews, I just like to say if I liked the book or not, what I thought of the writing style, if it held my attention, if it was an easy read, and sometimes even a little criticism if necessary. If it is an ARC or a giveaway I will definitely make mention of that and who I received the book from. 

What do you do to write a review?