Rather on the topic of the rights and wrongs of copying books, Baen Books has an interesting publication strategy. Its Baen Free Library makes available online selected works on its lists, primarily SF, arguing that the advantage of publicity for lesser-known authors more than offsets any loss from giving away the text free.
Keith Laumer (1925-1993) is one example. A writer who brought to his work an interesting background, an academic career followed by military and diplomatic service, he's little read these days. He wrote fast-moving SF stories and novels, in a hardboiled but, at its best, elegant style reminiscent of Raymond Chandler. The end of his life was unfortunately marred by a stroke that left him physically incapacitated as well as impairing his writing abilities (in which state -presumably his judgement was affected too - he insisted on reediting many of his works, to their detriment).
The Baen Free Library Keith Laumer section has several of his novels and short story compilations. Odyssey is typical in tone, featuring among other works the picaresque Galactic Odyssey (whose down-and-out hero shelters from a storm in what he takes to be a grain silo, only to find he has stowed away on a spacecraft). Laumer did humour too, satire on bureaucracy being a strong theme, as in In the Queue, Placement Test and the stories of the galactic diplomat Retief.
I was reminded of Laumer from running into the website of his brother, the late March Laumer (Wikipedia link - I won't link direct to his site, as it throws up popup ads). March Laumer wrote largely self-published reinterpretations of the Wizard of Oz mythos, some recycling characters and scenarios from Volkov's Russified versions. His novels were controversial for introducing adult themes such as the sexuality of Oz characters, thus taking them out of the genre of children's fiction.
Neverthless, other authors have done similarly: Philip José Farmer's A Barnstormer in Oz introduces Hank Stover, Dorothy's son, who flies his Jenny biplane into a green cloud and arrives in Oz to find some surprises. One is that it exists; another is that Baum bowdlerized its culture, not merely for sexuality but also for its social and political complexity. The book is discussed at the Reviews Page at the official Philip José Farmer site.
Different in tone, but equally mature in its themes, Gregory Maguire's Wicked: The Life and Times of the Wicked Witch of the West, takes a revisionist slant on the Oz mythos, telling of Elphaba, a green-skinned political activist who is ultimately murdered by the alien girl, Dorothy. Maguire goes into detail on the moral and political themes: for instance, the rights problems raised by the co-existence in Oz of animals (the ordinary kind) and Animals (ones with human intelligence). I read it a while back and thought it took itself a little too seriously, coming with its own Study Guide to the moral issues, but it's still an intriguing take on the mythos.
The Royal Timeline of Oz has an extensive collection relating to the literary history of Oz and its various spinoffs, both faithful and revisionist: see, for instance, The Dark Side of Oz and Beyond the Deadly Desert.