This is my first day here in this forum and this is my first ever post. In fact, this is also the very first thread that I opened thanks to the title of your thread. Well, I can't claim myself as an expert but thought I should also tell you what I felt after I went through your site. I'll keep it short.
I actually couldn't figure what your site is about ? Well, it seems that you are giving away ebooks for free. But for that you are asking your visitors to sign up for a membership. I am a bit surprised to see that it isn't a simple opt-in form but a membership sign-up. I was ready to opt-in but hesitated when I realized that it's a membership. What I mean to say, don't you think it a bit optimistic to expect people sign up for memberships that are easily available everywhere on the net ?
I also think (please don't mind) that the site doesn't look very professional. The header graphic has nothing to do with the subject matter of your site. And it would have been better if you could have it inside the rounded corner background box. You can also get rid of the Table borders (Don't know if you kept the borders deliberately).
You can see that I just repeated what others said. But hearing the same from more and more people might urge you to do whatever you need to do.