A friend bought me an interesting book called 'The Complete Merde' which is two books in one ('Merde' and 'Merde Encore!'). It has alot of slang words (argot) for everything, and shows how the French clip bits off words when they speak. Eg. t'as instead of tu as, and chuis instead of je suis. Since reading it, I've noticed loads of new slang words, so its quite useful. It also helped me in my exam, when they called a job 'le boulot', which I wouldnt have known otherwise. Its also funny to read, so I recommend it!