The book is marginally useful—maddeningly frustrating by repeatedly ducking at least one foundational issue, while making a quite helpful contribution to the indefatigable specter of legalism. Maybe we'll get back to that later. Written in 1954, it feels a bit dated.
But one little snippet just about knocked me out of my chair towards the end of my recent re-read. Let me just say first that McClain is no junior varsity Dispensationalist. His The Greatness of the Kingdom is a Dispensationalist classic. He's actually much more thorough and persuasive than some of the more widely-known Dispensationalist authors. And he's highly regarded by Rolland McCune, who—perhaps more than any other living theologian—represents the Dispensational wing of the Dispensational Party.
So here's what McClain had to say:
I would like to encourage Christians who delight in finding the Lord Jesus Christ upon every page of Scripture. Do not permit yourselves to be frightened by those over-cautious souls who cry against what they call "too much typology." Doubtless there are some things which may properly be catalogued as "types" and the others not. But whatever you may call it, it is the privilege and highest duty of the Christian to discover and behold the face of the Lord Jesus in Scripture—everywhere! Far better to break a few rules of classical hermeneutics than to miss the vision of his blessed face. (67-68, emphasis added)