Now I'm not sure it was the problem. I found a few books to delete, but not many, and only 2 in the offending genre.
Oh well, tidied it up, so will see if I still get the emails.
Other thing to try:
Go to Your Account and scroll down to Message Center. On the US site, there are a couple of links on the right side of that section that you can tweak. The Email Preferences and Notifications is pretty basic -- email or not and what address.
The other one, Amazon Delivers Email Subscriptions, has a whole list of genres, products, etc. for which there are newsletters. You can decide which ones you want to subscribe to. I think that these are sometimes turned on automatically when you buy something, which is why you may not remember subscribing to them. But any listed there are ones you ARE subscribed to and can turn off.
Down below that list is a link to browse all available subscriptions, so you can turn on others you might want instead.