You can learn a great deal about English and Tasmanian history. If you're wondering about its historical accuracy, Matthew Kneale spent six years researching this book, so he is clearly not a historical hack. Many reviewers emphasize Kneale's concern with the state of the aborigines after the colonial invasion. While that is certainly one of the focii of the book, there are large sections also devoted entirely to the English characters. Overall, the book maintains the tone of black comedy, much like Catch-22, although the comic element is subtler.
In essence, the story is about an ill-fated voyage involving a Manx ship and crew trying to smuggle contraband brandy and tobacco into England, but end up being chartered to Tasmania by some Englishmen on an expedition to find the Garden of Eden. It is a crazy premise with fittingly crazy results. The story is by turns funny, touching, and just plain sad. The subplot of the book is the English colonization of Tasmania and the ill-treatment of the aboriginal Tasmanians. The author appears to have done his homework, as a large part of the book concerns the history of Tasmania and its people through the middle of the 19th Century. One of the main characters is a native Tasmanian, and while the creation of such a character is mostly the author's imagination (as there are no real native Tasmanians left), he creates a touching portrait of person facing the exinction of his people.
The middle of the book bogs down a little with some interesting side-stories that are not directly realated to the plot (hence 4 stars), but the end is worth the wait. I think Capt. Kewley is one of the most interesting fictional characters I have come across in a long time. Read this book--it will make you think.