If you want to link your book (or other books) with books that are already selling well, use the Wish Lists and Recommendations features, and in your customer reviews you can create a link using a special format to point to another book at Amazon (there's a button for doing so when writing your book, which is easier than remembering the syntax.)
Just be very careful about how you link to other books, and I generally don't recommend doing it to your own books because that seems a bit sleazy and is against the Amazon terms of service. Technically, if you have any sort of financial interest or competitive interest in a book, you can't leave a review, and Amazon will take your review right down. In fact, they will sometimes consider the fact that you sell any book as a competitive interest, even if you sell science fiction or fantasy books and you want to review a book on gardening, for example.
Enforcement of that rule is inconsistent, and hopefully they'll come up with better policies and stop deleting legitimate reviews and get rid of the “paid for” reviews instead. In my mind, the best way to use the product tagging feature is to:
- Use it whenever you think you can legitimately help somebody reading that review by pointing to another product that isn't one of your own.
- To make friends in the Apex Authors Facebook Group and to buy each other's books when they are on promotion and to leave honest reviews. (Unless the book needs some work, in which case talk to the person offline and don't leave a review.)
- To have others use the linking features in reviews to your books and for you to reciprocate for their books. Again, only do so when it will legitimately help the reader of the review and is above-board. In fact, keep an eye on the books being promoted and just add in any that should be mentioned whenever it's appropriate, whether that person is reciprocating or not.