Just quickly, I wonder if anyone is willing to offer a view on this one. (Hint: books by present company, such as Kong Reborn by Russell Blackford, do not count.)
The Future of Human Nature by Jurgen Habermas must go very close. I'm re-reading this, in the wake of recent discussion about Fenton's critique of Habermas - I hadn't read it for a a year or two. In that time I had forgotten what an execrable piece of bio-Luddite rubbish this book really is, committing just about every possible sin: it is repetitive and badly structured (even within the individual pieces from which it has been cobbled together), relies on sonorous rhetoric, rather than careful, rational analysis, is full of bizarre logical non sequiturs, projects an almost mystical view of human nature, and just generally is one book you would not want to give as a token to a favourite smart adolescent (or anyone else).
Any other suggestions?