A good first line is not always necessary because who stops reading after one sentence? But it can be extremely useful in building expectations for the style and characterisation that will follow. While book jackets can indicate a broad genre, that line can define the subgenre.
The opening may establish the tone, character, location, era or season but it can also pull a reader into the realm of the story that follows, and often into the head of the protagonist or into an alternate reality. When we open a book, we are ready to embark on a journey. The starter pistol should propel us forward. In my experience, a great opening will also raise questions that needs to be answered. Who or why or how or indeed, wtf?
