If you want a short novel in relatively simple language, try Siddhartha by Hermann Hesse, The Alchemist by Paulo Coelho or Billy Liar by Keith Waterhouse. Maybe the Hitchhiker's Guide series by Douglas Adams.
Crime and Punishment, one of the best novels ever written but quite a difficult read. If you want an engrossing story and are up for a bit of a challenge, highly recommend it. But on the other hand, if you struggle to stick with a book, having to continually look up in the footnotes what Dostoyevsky was referencing will seriously put you off.
Also I strongly feel the short story format is very overlooked nowadays, particularly in context of our short attention spans nowadays. Some good anthologies are:
- The Wonderful Story or Henry Sugar (and 6 other stories) by Roald Dahl (as long as you don't require all literature ever written to have been produced by people whose personal views match your own);
- Septuagenarian Stew by Charles Bukowski (as long as you don't require all literature ever written to have been produced by people who lived puritanical existences). This is a mixture of poetry and short stories;
- The Loneliness of the Long-DIstance Runner by Alan Sillitoe;
- Portrait of the Artist as a Young Dog by Dylan Thomas (again with the caveat about the author being puritanical);
- The Madman (His Parables and Poems) by Kahlil Gibran if you feel you might enjoy some rather poetic, partly philosophical and partly nonsensical short stories.
I had a really interesting anthology of Japenese folk stories I got for 50p from a charity shop a few years ago, which I'd have recommended too but lent it to a mate about 2 years ago and haven't got it back and can't remember what it was called.