The Complete Merde! by Genevieve, Michael Heath

I can see why they've chosen this book for the site as it really is an indispensable guide to French argot. I bought it a few years ago and I still refer to it. The use of slang in any language is something that changes constantly as words go in and out of fashion or become less or more acceptable e.g. the use of the word 'pédé' for homosexual is now not acceptable in French society (so my French friends tell me) whereas the use of 'merde' is now almost universal. In an effort to be comprehensive, so many dictionaries of slang end up confusing the user as they fail to convey which terms are old fashioned and which are bang up to date. I like the Complete Merde because it is themed around the key words that form the essential building block of so much French slang .e.g. merde, con, foutre, ficher etc. This guide will give you all the nouns, adjectives, verbs and adverbs formed from these words. Arranging the book this way also makes it much easier to learn and absorb the vocabulary. The book also has some good sections on argot for parts of the body and the most commonly-used idiomatic expressions, particularly those that involve animals. If you only want to buy one book on slang, this is the one to go for!