Literature
Although the Robert Fagles translation is modern, popular, and easy to understand if you've never studied Greek, Richmond Lattimore's classic translation captures the feeling of the original Greek more accurately.
1984 and Animal Farm are classics, but a much more accurate portrayal of contemporary life than 1984's 'Big Brother' is the middle class despair captured in Orwell's Keep the Aspidistra Flying.
Amy Heckerling did a great job of updating Emma into Clueless, but she lost the powerful subtlety of Austin's novel by entirely eliminating certain things, like the character of Mrs. Weston -- the wise governess and Frank Churchill's mother.
Boston University has worked hard to collect documentation of 20th century authors; for my personal tastes, I prefer Yale's collection of documentation of 18th century authors, and Harvard's of 19th century ones.