Hey pikka,
You can actually use both rel=next/prev and rel=canonical on the same webpage, but you have to be careful on how you use them.
If you don't have a view-all page, then DO NOT use rel=canonical on the review-pX page to point to the main product page. That's like saying "This page has identical content as the other one, so please disregard this one and use the other instead". It's somewhat of a 301 redirect, which would DEINDEX your review-pX pages.
However, using rel=next/prev is perfectly fine, and it's actually the recommended method when there's no view-all page. You can still use rel=canonical but only to point to the current review page (so basically you would use this just to filter out session IDs or any other parameters that lead to duplicate content).
So, in your case, you should use them like this (let's say we're on page 3):
<-- current page, "clean" url
<-- previous page, can contain parameters
<-- next page, can contain parameters
Do NOT use this:
Hope this helps, here's the Google support page on this issue and Maile Ohye's excellent video explaing it.
PS: Almost forgot, regarding your avatar: