This old Russian classic SF is surprisingly relevant and fresh today, sans all the copious amount of smoking going on. :) If anything is going to give this little gem away, it's pretty much only that. 
 It's very tight, masquerading as a scavenger adventure that becomes a black-market thriller that becomes a Question about the nature of intelligence, discovery, and even the most basic question of all: "What the hell are these aliens thinking???" 
 After all, they just left a huge mess by the side of the road, not even bothering to say hi to the damn locals before dumping their half-eaten crap and leaving their high-tech soda bottles. 
 I mean, seriously? Who do these Americans think they are, despoiling such a pretty Russian countryside? *sigh* And then there's the whole mess about consumerism and capitalism, giving us a pretty complete and coherent condemnation while never quite "saying" anything. It's all just shown, and shown extremely well. 
 And then there's the now obvious connection to the much later work that is heavily indebted to Roadside Picnic, the redoubtable Area X: The Southern Reach Trilogy. Others have gone over the connections better than I will, but I can say one thing freely: The two are very similar in the gross, between the oddness within the area and the desire for both understanding and possible trinkets, but that's pretty much where the similarities end. Sure, we'll keep asking questions in both novels, long after they've ended, but this one keeps things pretty light even when the MC is crawling through the mud. I blame it on the alcohol. But then, this is very much a Russian novel. 
 I think I might go ahead and say that I think this one is the tighter SF story. The first novel in Area X was delicious for the surreal and the details, but this novel had a lot more action and straight talk for those who prefer their tales snappy. Don't be surprised, though, if you get more of a bellyful of the evils of capitalism rather than a deeper exploration of aliens and our own ultimate insignificance. It's there, but the sneaky diatribe against the West is actually the superior portion of the novel. (Superior both in fun and plot and the things that our MC must endure, rather than sheer page space.) 
 This is quite an awesome classic SF and I heartily recommend it. It obviously had a lot of love and care poured into it, and the results are fantastic. :)