Roadside Picnic is better because nobody in it understands the Zone
Also a note on which translation you are holding
Nothing in Roadside Picnic is ever explained, and that is why I keep going back to it. Aliens stopped somewhere in the countryside, left their litter behind, and moved on without noticing that anyone lived there. You never meet them. You never find out what the objects are for. The book is better for both.
What the Strugatskys spend their pages on instead is the people living at the edge of the Zone who make a living carrying things out of it. Redrick is a smuggler with a family and a shrinking set of options, not an explorer with a mission. The strangeness stays strange, and the story is about what it costs to work next to it.
It nearly did not reach print in that shape. The novel ran in a magazine in 1972, and the book edition sat blocked for years while the publisher pushed for changes the brothers would not make. What finally came out in the Soviet Union was cut. The newer English translation puts back a good deal of what that edition lost, so it is worth checking which one you are holding before you decide the prose is flat.