Is the font size in the book same as the sample text? Well, I kind of expected more for an E-book.
For example, you can make font size as large as Steve's blog posts or you could make font size to about 12-14 in Times New Roman with neat spacing.(Iam assuming the the quality of your book is same as the sample pdf. So let me know if the quality of the book is more than the sample)
This is just my opinion.