Bridget Jones's Diary by Helen Fielding (1996)

Chick keeps diary of alcohol use, weight gain, workplace drama, and romantic troubles. Loosely based on Pride & Prejudice. The book that started it all. Utterly hilarious and utterly re-readable. 

Followed by Bridget Jones: The Edge of Reason, based this time (even more loosely) on Austen's Persuasion. Noteworthy for the utterly hilarious scene in which Bridget Jones interviews the actor Colin Firth about his role as Mr. Darcy in Pride and Prejudice.