As the name already suggests, 20 Weird, Irradiated Encounters provides you with an list of themed encounters that you may use as a random encounter table. Not all of them are detrimental, included are:
Harmless, scenic encounters (well, harmless on their own, that is!)
Encounters build around mutant-beasts that are not part of the Mutant Future core rules
Two encounters build around “old friends” from the Mutant Future core rules.