Marshall over at the Campaign for the American Reader has an interesting "test" - inspired by Marshal McLuhan, according to an early post - for books: Readers should turn to page 69 and have a peek. If that page hooks them, presumably, the book is worth checking out. he's devoted an entire website to the proposition.
It's a fun concept. I think Helios passed - though maybe not. (Here's my entry - or perhaps defense - of my page 69.)
I wonder, though: what's the equivalent for e-book versions? Or audio?