You shouldn't really be thinking about what YOU think sells well but what sells well on Amazon. Look at keyword research tools to find buyer intent keywords with high earning potential.
ANYTHING they buy, as long as they have their 24-hour cookie still, will count toward a sale, and a commission for you. It's unfortunate that the buyers only bought e-books. You want to have what your visitors are likely to buy. If your visitors are all about kitchen appliances, then you could do a few actual reviews of kitchen gadgets, for example. I don't know how you're getting your clicks, but try to target your visitors.
If you want long time affiliate . then you go with kitchen appliance. keyword research is more important for amazon affiliate
When I had a autoblog some years ago, products pages that rank in google usually sell. So if you can rank a product name page in Google, that will sell.