This book was similar to Annihilation, in that much of it is about people exploring an alien and hostile environment. In this case the environment was the scene of a brief alien visit (the Roadside Picnic of the title), where the aliens left behind various bits of their trash and pollution. Even the alien's trash and pollution is immensely valuable though, and demonstrates concepts far beyond human science. However, for this same reason the picnic grounds are immensely dangerous and unpredictable, as even common objects in the zone might have been tainted/changed by radiations we can't even measure yet. Entering and exploring the zone is a bit like reading SCP entries written in the 1970's. The non-zone parts of the book are fine, but suffer a bit from being written 40 years ago, which is why wouldn't rate this as 5 stars. Still, for the time period this book was written in it was extremely original and inventive, and 40 years later it is still a great sci-fi story.