"Flying the big jets" is what it says on the cover - an introduction for the layman on what it is like to fly a big jet. If you aren't a layman (i.e. you have any type of pilot license) then it won't be of much help to you. (It's a good book for what it tries to do, though - explains the life and operation without dumbing down the subject.)
"Handling the big jets" is a much more technical work, and much more interesting (and really the only one of the two you would want) for those with a professional licence.