ProDigit, you seem to be thinking up every excuse under the sun for not using CSS, when it's hugely beneficial to do so. Having all your formatting instructions together in one place is enormously easier than applying formatting separately to each element in the book.
By having a CSS definition for your <p> tag you can instantly change the spacing and indentation for every paragraph in the book by editing one definition in the CSS. Surely you see the benefit of this compared to having to edit every paragraph individually if you want to change its indentation?