Recommended by a colleague, I borrowed this from the library yesterday and finished it this morning. It's a straightforward book, but has a lot of insight into the way that marketing works in big companies, and what might explain the wrong steps that have been taken.
Showing its age in some ways (it's from 1994) - the computer industry discussions are peppered with words like "mainframe", and "NeXT" workstation, and while it gives credit to Steve Jobs as a great presenter, he's not part of the big picture at all.
The strongest ideas are in terms of brand dilution ("the law of line extension") - a company that's successful in one area will always try and spread into other areas, often costing market share in both. A short, but useful read.