Some of the themes the book deals with are:

1. The human fascination with the unknown
2. The cosmos as a mystic source of power
3. The existence of a higher thinking civilization
4. The minimalism of humanity
5. Civility vs. chaos
6. Known vs. the Unknown
7. The human need of control
8. Master vs servant behavior
9. The search for true happiness

The civility vs. chaos theme is notable in the actual name of the story. The title Roadside Picnic is a metaphor that shows how the aliens came, chose a spot to land, spread out their artifacts, then took off and left a really big mess of their stuff behind for us humans to Stalk. In the midst of this chaos, humans still must strive to survive and somehow overcome this insane moment. This is why it is a constant battle.

The human need of control comes as a result of looking for the artifacts, and the powers that such artifacts have over people, from changing their appearance, to controlling the laws of gravity. They go at crazy extends penetrating the boundaries of the Zones to get to these artifacts. Many found their deaths in them. However, the need of control is so intense in human nature that even death wouldn't move convince them not to enter those areas.