What is the author's style in Bridget Jones's Diary by Helen Fielding?

The language in this book is very casual. After all, it is a collection of diary entries. For example, there are entries where Bridget lists what she has eaten and the quantities. Not really central to the story, these are still entries one might see in a diary. The casualness of the language lends to the honesty of the book. The author even goes so far as to create a personal set of abbreviations that are unique to her.