How to ask if a book was written with AI?

I’m currently reading an ARC I was given in exchange for a review. Pretty early on I noticed some things that are consistent with AI generated writing. I brushed it off at first, but I’m almost finished with the book now and it’s like every single paragraph has something that raises red flags. I am obligated to finish it and leave a review but I’m wondering if I should contact the author first? If so, I’m not sure how to ask because I don’t want to offend her and I would feel bad accusing her of it if it’s not true (I’m a very socially anxious person so just to contact the author in general is scary) but I also don’t want to promote something that is AI generated. How can I ask in a polite way, or should I just give her the benefit of the doubt and review the book without mentioning it?