There are different ways to do research to see if you have a winning e-book or not. By the way, you mentioned setting up 2 or 3 sites. If I were you, I would just start with one and when that is making a profit, start a second, then a third. It's always best to concentrate all your efforts on one project at a time, but, that is only my opinion.
You can do market surveys by direct mail or via the internet or face to face in your local area. I will just talk about the Internet here.
#1. Create a survey form asking people questions about your product to see if they would be interested. If you already have a newsletter subscriber list, send them a request to complete a survey on your product, in return for something free (free report, discount on the product etc.). Don't ask too many questions (eg. 10 should be good) and leave room for the person's own comments.
#2. Set up one site and create a pop-up window that shows up when people leave your site. It would ask people to click on a link to your survey form - again if they fill it out, they get a good bonus from you.
#3. Place ads in newsletters (preferably in your target area) asking people to participate in your survey
in return for a reward (bonus).
When you get an adequate number of replies (eg. 50), see what everyone says. If they like your product idea, create the e-book and post it at your site with proper copy and an ebook cover graphic.
Start advertising and also send the people who replied to your survey their bonus and an offer to buy your book, at a discount, preferably.
You can also ask Ken Silver or Ricky Higgs for advice in this area. They are more qualified than I am. You should also take their courses, because they are low priced and extremely good.
There is no better idea than studying everything you can get your hands on and putting it into practice. It may take a while to work, but, a person learns as they go on their journey to Internet Success. It isn't easy, but, it is surely worth it.