A serif font style is easier to read in body copy than a sans serif style.
By Winter 1964, the The in the title disappeared, and the shortened name got a serif type treatment that endured for a decade.
Large blocks of small text, such as document body text in printed documents, are easier to read if serif fonts are used.
Meanwhile, many texts have been happily read in sans serif typefaces, and other texts are hard to read because the serif typeface chosen is just plain hard to read, or badly set.
The font used on the cover and throughout the book is a serif font with distinctive, thick slab ends - a kind of conservative font appropriate for a school textbook.
Almost all use a serif face for body type.
Most importantly they don't have the resolution needed to properly render highly legible serif typefaces like Times and Garamond.
Headlines are split between serif and sans serif faces.
A serif face would have been gentler on the eyes, although it would have probably taken more space.
More superficially, I like paperbacks, modern typefaces and striking covers, though I dare say I should attempt to retreat from my prejudice against anything written in a serif font in favour of more considered judgements on content.