This is pretty easy to fake, so you yourself should only read reviews of people who do give a con for the product. For example my ex-roommate published a book but got 2 pretty bad reviews among total 5(?) books sold.
So he himself wrote about 10 5-star reviews for his book.
You should always check how many reviews has the person given previously. If it’s more than 5, generally that’s good enough.
P.S.: Ironically the book was about honesty in our life. I can’t tell the name but I got many laughs due to this incident.