I think it depends on what you want to do with the rating information. If you want to show the most popular sites/books, a simple liked/dislike system is probab

I think it depends on what you want to do with the rating information. If you want to show the most popular sites/books, a simple liked/dislike system is probably sufficient. I think the 0 to 5 scale is more helpful if you want to be able to recommend similar products. You can do that with the like/dislike system too, but I think you get better results with a more granular scale, Reddit's recommendation system, for example, is famously unhelpful.