I've always been insecure about some everyday words like `Luddite' and `egregious' and `invidious' - but the problem was I never got around to looking them up.
So I was delighted to discover this book which positively brims with all these words that were foxing me.
For example, I've read some of George Orwell's novels, but when someone described a situation as `Orwellian', I never knew exactly what this meant. It turns out the word doesn't refer to `Animal Farm' (as I thought it did) but exclusively to Orwell's novel `1984', and so `Orwellian' means `contrary to the well-being of a free society'. This is a classic case of thinking you know a word and so never looking up its exact meaning.
I did already know about 5% of the words in the book but language is such a subjective thing that I guess one book is never going to provide you with every single word you don't know.
And when I have friends over, this book inevitably gets spotted by someone and out it comes - it's a great icebreaker to pass around the table after a meal and get people to select a word and then see who knows the real meaning.