This is an older book - over 20 years old. I knew going in that it would be dated, especially since it deals with tech details of getting type on screen. As such, some pieces no longer apply.
However, I wanted something that got to the fundamental principles of getting typo on screen, and in that sense the book offers some really interesting insights. There is some real gold in here that is timeless, both in terms of the history of type and why certain things are done the way they are as well as some good research cited that actually quantifies things like how reading speed or comprehension vary with, say, margin width or line leading (just to name two examples - there are many).
I also really liked the list of suggested areas for R&D - sort of an unsolved problems list from 20 years ago, many of which still apply.
Digital Typography: An Introduction to Type and Composition for Computer System Design