The meme going around in my grade school so very many years ago was that English is one of the hardest languages to learn. It turns out that that is completely not true. In fact, English grammar is one of the simplest there is (Persian being another). If you want a language that’s really hard to learn, look at languages that are spoken only within very small, insular societies; languages that aren’t influenced by an influx of adult learners. There are languages in which virtually every verb is irregular; a language in which there are not just 2 noun genders (as in the romance languages) or 3 (as in German), but 10! Languages in which plural forms of nouns bear only the slightest resemblance to their singular form. Any kind of complexity you can think of, and lots that would never occur to you: some language has it.
So McWhorter talks about the nature of language, how languages evolve, how they accrete features and complexities, and how they get simplified if they are inundated by foreign adult language learners.
This is all pretty fascinating stuff, if you are interested in language.
One thing that was a little distracting about the book is that McWhorter’s writing style wanders all over the place. In one paragraph he’s academic and formal, in the next he’s completely colloquial. He injects odd parenthetical comments where they are not needed. It can be a bit distracting.
But he certainly knows his stuff, has a point of view, and provides plenty of interesting examples to bolster his theses.