The people who read Coelho are those with glasses that half full. They probably read Eat Pray Love and The Secret and listen to Josh Groban. And watch Oprah. They most definitely post inspirational quotes on their Facebook and twitter.
The people who read J.D. Salinger think that they have existential crisis with philosophical potential that might give either enlightenment or falldown for the humanity.
The people who read John Grisham have this illusion that good guys always win. They probably have grandchildren. They most likely read Agatha Christie as well.
The people who read Harry Potter in the early 2000s probably never read anything longer than celebrity exclusive interviews in their favorite magazines. The people who read Harry Potter now are either a) have a major crush on
The people who read and like Dan Brown are generally not really into conspiracy theories. But if it's presented to them from the point of view of a leading Harvard symbologist and a bio-entanglement physicist, suddenly it becomes totally make sense.
The people who read Christopher Brookmyre see themselves as geeks, have a good sense of humor and musical taste (e.g. nods whenever someone bashing Oasis), witty, skeptic but open-minded. Other people see them as pretentious douchebags who bitch about other people's favorite authors.