But trustpilot reviews are not meant to be written to 'Which?' standards. If that is what you want consult 'Which'
I certainly do not write a huge tract when preparing a Trustpilot review. I give the stars and then highlight the best parts, occasionally the failings, I resume people can work out by the number of stars I give what quality of overall service I received.
On books, it rather depends where you are reviewing the book. On Amazon, I think reviews should be short, may be only a few lines. When I buy a book I really have no interest in what other people I do not know thought of it. There is clearly a reason why I want to read it, and that shapes my buying decision. However it does help to know if the supplier was dilatory or rude, when I followed up a late delivery, or whether it was damaged in transit.
On a book review site, then obviously I want a considered literary review.