They’ve tallied more than 60,000 votes from their fans on top science fiction and fantasy books. The rankings are a bit odd, in that they include votes for groups of books as well as votes for individual books from various series.
Given the voters were self-selected from among those who either listen to NPR or were directed to the voting by people who do, there were a few surprises in the results, like finding Robert Heinlein’s Starship Troopers clocking in at #31 and The Moon Is A Harsh Mistress at #34 (Stranger In A Strange Land at #17 was less surprising).
There were a few books I’ve never even heard of, like The Kingkiller Chronicles, by Patrick Rothfuss at #18 and The Mistborn Series, by Brandon Sanderson at #43.
I think it’s a pretty fair list overall, although I’d quibble about some of the individual rankings. On a quick count, I’ve read 16 of the top 20 (but only 50 of the entire list).