Tommy by the who. A really incredible story. Quadrophenia (also by the who) perhaps could be listened to in one go, but it just doesn't have the same power behind it. Sure, a quad-split-personality is a great subject to explore, but Tommy tells a better story. The music is excellent in both however.
Also, The Wall is another great choice for something like that. A truly great motive behind that rock opera, but I think it would be better stoned. I can understand what they're saying about not living behind a wall, but I haven't tried it high yet, to sit down to listen to the whole thing anyway. It truly is magnificent, but it might be better with an additional bag o fun included.