When you write about drinking, you never run out of material, because you can go on to writing about quitting. And if that's not enough, write about falling back into drinking, then how quitting the second time is different, going back to drinking responsibly, how that doesn't work, quitting again, etc. etc. Drinking is a goldmine of subject matter. And I bet drinkers are a good source of readers, since you can drink — quite a lot — while reading.
ADDED: We could make a list of books about drinking. The 2 that sprang to mind for me are:
"Dry," by Augusten Burroughs
"Clapton: The Autobiography"