Just my 2 cents idea :
Beccause we could want to share our opinion/experience on other differents things (sites, certification...) why don't we simply add a sub-category in review (2 existings are book, modules) anyone submitting a review can type (text input) the subcategory then the review...
If we manage to get people smart enough to reuse existing sub-category (no 'books','good book'...) it could be efficient (in the sense of ordering the information) and easy to modify at the same time...
"Trying to be a SMART lamer" (thanx to
Merlyn ;-)