I'm going to offer some friendly criticism on marketing. (I can't really comment on the content of the book, given that I haven't read it.)
- Invest $50 and buy a nice Wordpress theme off of ThemeForest, because junior software engineers are picky folk. If it nets you two more sales, then it's already paid itself off.
- The table of contents tells me what I'm going to learn from this book, not why I want to learn them. Often, the answer to "why" is either "to make a lot more money" or "to build a lot of cool things I wouldn't otherwise." The three points you outline underneath the ToC hit those aspects much more strongly, so I'd move those above the fold.
- Throwing up an email list where you send me some snippets and then try to upsell me is advised. I haven't heard of you before, so I'd prefer some credentials before I commit to a purchase (remember, I'm a junior software engineer, so both time and money are scarce resources.) Testimonials would also be helpful here.
- There's nothing wrong with a second call to action at the bottom of the page.