Arika Okrent has written a fascinating book which reveals the obsessions, motivations and sometimes self-destructiveness of the men (and they are usually men) who have felt compelled to invent their own languages. Of course, Esperanto is in here, but it's the other languages that stick most in the mind, such as John Wilkins' idea that words ought to link form and meaning - so that the word itself tells you what it means - or Brown's Loglan, a language designed to remove the ambiguities inherent in human languages, by allowing only logically precise sentences. You would imagine that Vulcans would speak such a language (maybe they do!) but it's the Klingons who get airtime in this book. Yes, we all know how sad they are, those who attend Star Trek conferences with plastic mouldings on their foreheads, but did you know that Klingon looks like a real human language (albeit a very odd one)? I really couldn't put this book down - it was such a great read. If I have any criticism at all, it's that there just wasn't enough about the grammar of each of the invented languages described. I would have liked a syntax summary in the appendices for each of the languages, so as to get more of a flavour of the oddness (or otherwise) of each of them. But that's really a minor point, as we can all go and look them up online if we wish.
So, do YOU have the "secret vice"? Have you ever dabbled in made-up languages? Go on... admit it! You're not alone, you know! They can't arrest you for it!