Personal favourites: The Jungle, exposing the squalid, sordid condition of Chicago's meat-packing industries. If you're a fan of Harry Turtledove's slightly odd alternative American history, he was the President of the US from 1920-28.
If your literary tastes stretch from socialist muckraking to jolly-hockey-sticks girls' boarding school japes (and I know at least one comrade to whom this applies), then you'll be sad to learn that September 20th is also the anniversary of Elinor M. Brent-Dyer's death in 1969: author of 60 Chalet School novels. The school itself, under pressure of political events, moved from Austria to Guernsey, thence to two places on the English-Welsh border, then finally to Switzerland. Interesting how many tax havens featured… They're fascinating tales of how rebellious girls have their spirits broken as they learn to conform to the rules of a snobbish, elitist but apparently kind-hearted meritocracy.
Interestingly, there's an unofficial - and rather misanthropist - sequel, The Chalet Girls Grow Up which sounds far more interesting:
A book that updates the stories of The Chalet School Girls into a world of sex, drugs and illegitimate babies bringing characters into the present day with references to Vietnam, Soweto, Greenham Common and the Falklands War.Poor Elinor must be spinning in her grave.
Update: lo and behold, here's hard-boiled crime writer Val McDermid talking about the Chalet School novels as her inspiration on Radio 4 (brief review here)