Sakhalin Island by a relatively young Chekhov is a must read. The book provides so many insights into Chekhov, and as Robert Peckham noted in his review altered the author's writing style leading to the great literary works that followed. Peckham further notes,
Sakhalin Island focuses as much on a moral and conceptual geography as it does on a physical location. Throughout the book Chekhov demonstrates that for most of his contemporaries Sakhalin was less a place than an imaginary topos; because it had acquired mythical status, its existence had become fictitious. Significantly, Chekhov observes that the official charts of the Tatar and Sakhalin coasts are notoriously unreliable and that the captain of his boat 'follows his own, which he draws up and corrects while sailing.'