Two recommendations
1. POETRY: Poetry tends to be very short and so you can easily read at least a bit of every canonical poet in no time at all. Not to say poetry is EASY but you can get a sampling of - say- Coleridge, work out if you think he's any good, and explore his poetry in general if you like what you have read.
2. SHORT STORIES: Again, very short, and a lot of the big novelists also wrote short stories. You can therefore get a good idea of if a novelist is "worth" reading. You have to read literature for enjoyment, ultimately. There's no use forcefeeding yourself a 600 page victorian novel if you can't stand the author.
3. PLAYS: On the page, very short. This is one of the great things about Shakespeare - unlike George Eliot, it won't take you all that long to read all of his major works.
4. ANTHOLOGIES There are also lots of compendiums of important thinkers/writers you can dip into - I recently had a look in one of my old American studies textbooks and found an essay by Susan Sontag "Against Interpretation" which I really liked. I think I'll explore her other essays based on this.