This is a mixed bag.
The title and introduction promise us "interesting stories" about words, presumably their origins, development and usage. And sometimes we do get that. But other times, the entry is literally just the basic definition of the word/phrase. I ... could just read a dictionary for that?
Other times, entries left me with more questions than I started with, because the explanation used niche terms I also didn't understand. Or else they referred briefly to things I suddenly wanted to know more about. For example, I always thought the origins of OK were obscure, but Dent confidently states it's "an abbreviation of 'Orl Korrect' ... a facetious spelling typical of the 1830s". Were the 1830s known for facetious spellings? Who was doing it? Why? Now I want to know!
Other times I felt like we didn't get the whole definition. For example, the entry for "upstage" describes its literal theatrical meaning, then continues, "Coloquially, the term 'upstage' means aloof". This intrigued me as I'm pretty well-read but have never heard it used that way. Google gave me one example ("His upstage attitude made it difficult to approach him"), but I mostly know it as a verb, meaning to draw attention away from someone else to yourself. Yet that meaning didn't get a mention.
And finally, I have no authority to declare this book to be wrong, but the section on 'eggcorns' was bizarre to me. I was expecting, say, "pacifically" instead of "specifically", but instead we got "putting the cat [cart] before the horse", "cut to the cheese [chase]" and "going at it hammer and thongs [tongs]". Who says those? Never seen them once.