I've read, watched, and written a number of reviews myself.

If I may, I'd like to add a few thoughts to this:

I've heard YouTubers, who received advanced copies of a product, say, "This product was provided by X for the purpose of reivew," or something to that effect. I think it's a rule: if you receive an advance copy, you should state that in the review.

Usually, if I'm going to do a star- or point-based review, such as one on Amazon, I'll do my best to only pick books that are at least a 4-star. That's because, being an author myself, I know the amount of effort that goes into researching and writing, and I want to do all I can to sing the praises of a good book, while also gving hints to any minor shortcomings.

If, on the other hand, a book is, in my opinion, less than 4-star worthy, I may not leave a review (unless the book is so bad that I want others to avoid it). But quite frankly, I don't recall ever having to do that.