As @muppetish‘s answer implies, the story was originally written as a play and not as a novel. Before that, Peter Pan was apparently a bit player in a novel written for adults.
From Wikipedia: The character’s best-known adventure debuted on 27 December 1904, in the stage play “Peter Pan, or The Boy Who Wouldn’t Grow Up”. The play was adapted and expanded somewhat as a novel, published in 1911 as Peter and Wendy” (later as “Peter Pan and Wendy”, and still later as simply “Peter Pan”).
@Ltryptophan, what constitutes “best” to you? Oldest (earliest) printing, most authentic looking, finest stock and binding, nicest illustrations?