Have you made more money promoting one ebook on your site or selling multiple ebooks in the same niche by setting up a landing page which rates each product? I am trying to establish if it's a good idea offering a choice to the visitor. On one hand reviewing several ebooks makes you come across as being less biased, however is this detrimental by offering too much choice and confusing the visitor and they don't make a purchase at all? If you review several ebooks, is there a magic number?
I have sites reviewing just one product and I have site reviewing 3-4 products. My conversion is consistently better on the sites reviewing just one product - mainly because people were looking for specific information on that product and I give them that final push to whip out their credit card. There's money to be made in both models though.
It depends on the visitor. If they're looking for information on a product specifically, obviously you wouldn't mention other stuff. BUT if they're looking for general how-to info, a site comparing products would work better.
All about targeting, depends on what long tail keywords youre going for, obviously if youre ranking for water4gas youd want to talk about that, while new hho technology you might do better by reviewing a few and seeming like an impartial helper.