If you have only the second edition, you only have about half a book! In any event, when you play alone, it makes no difference if you play one hand (with the dealer) and bet x or you play two hands (plus the dealer's) and bet a total of 1.5x. Do you see that using 1.5x more cards (three hands vs. two) but also betting 1.5x as much (0.75x on each of two hands) as when you play one hand amounts to the same dollar profit per hands used?
However, the minute you have other players at the table, it becomes obvious that playing two hands is better. Do the math!
Don