Roadside Picnic, by Arkady and Boris Strugatsky. 1971. Russian science fiction novel.
Interesting setup, but didn't deliver sufficiently. It's a problem when the most engaging, ambitious and exciting scenes are the characters speculating about the wider mechanism and purpose behind the setting, in moments unconnected to the actual plot. Which is a shame because the book's take on alien encounter is pretty neat--as suggested by the title, the brief alien presence might be completely uninterested in humanity, just a brief tour, and the ultra-advanced technology left behind is nothing more to the aliens than the equivalent for a few empty cans. There's some real meat to this premise, and probably even more when it was first published, as a corrective to the common portrayal of humanity's role.
Unfortunately, most of the novel is a type of espionage-heavy thriller in terms of different factions trying to gain access to the super-advanced alien garbage. It's engaging in theory--taking a cynical but not unrealistic, and not excessively bleak examination of short sighted reaction to a transformative situation--but it fell flat for me in execution. Events seemed overly dense, excessively focused on the flat main character, and the pacing is odd. Above all there's a sense that the story we're given isn't the most interesting one set in this universe. Certainly at times the book calls out for a larger scale, for it to consider wider humanity and their role in the cosmos for the plot rather than just in speculation within the story.
Similar to and better than: Robert Charles Wilson's Axis
Similar to and worse than: Strugatsky's Prisoner of Power