Best not to sneak an email collection scheme in on people even if it really is only for your newsletter.
Most people have more than enough spam in their inbox already, if someone wants to get updates it's very easy for them to just click a button that says "Click here to get updates".
Email for updates being a foot in the door for further communications is pro forma and legally regulated. I think you're unnecessarily suspicious.
Even if it isn't nefarious, it's often unwanted. I usually turn around if I have to provide my email to see some sort of whitepaper or sample because it means I will have to later unsubscribe from whatever email list I was put on and hope they don't share the list with others (which happens, often).
If only there was an email service that let you create multiple email addresses for free! Or better yet one that let you create an email address that only exists for 10 minutes. A 10 minute mail service if you will.
Whenever someone asks for an email, I just type lalelu@yopmail.com, and then I go to http://yopmail.com/lalelu and click the activation link.
It's a beautiful service.
Basic marketing to sell the book...don't be dense
The background image in the e-mail collection form can be opened in a new tab. It's full-size, so you can see the ToC without buying to book or signing up.