The interior of your book is just as important as the cover.
Once your book is purchased you’ll need to hold the readers attention. Certainly good content has a lot to do with it. Good editing and proofing as well.
But the real reading is done from the type that is set… formatted, sized and styled to hold the readers attention and make them feel comfortable and not want to put your book down. We have been “taught” by exposure to feel comfortable with reading a typeface with “little feet” otherwise know as serifs. Typefaces such as Times Roman and Garamond are know as serif faces and when used for your interior text will give your reader an easy read. Typefaces such as Ariel and Futura are known as sanserif (without little feet) and are best used for heads, subheads or chart and graphs.
Be sure to request test pages of your text layout for your approval before your book is formatted.