The wasps who have taken over Julia have an ancient enemy: a race of spiders who are normally a prey animal for the wasps (the wasps lay their eggs in the spiders, who are then compelled to spin a kind of nursery for the larvae, who eat the spiders on the way out). These spiders are an ancient, collective intelligence, and they use their power to spin facsimile humans ("men of indeterminate ethnicity") who form a spy network that oversees the human race and invisibly fights off the wasps' influence, in an ancient battle that has been waged for the whole history of our three species.
Sensation is told from the spiders' collective point of view, as they attempt rescue Julia from the wasps' clutches and stash her in the Simulacrum, a network of places, retailers, and lifestyles that don't ever mesh with the real world. It recounts Raymond's fraught relationship with the movement and its non-founders who refuse to plan, or take on any sort of authority structure.
Mamatas is a powerfully acerbic writer, both in fiction and online. His acid wit is infamous, and it is on splendid display in Sensation, which is alive with scornful insight about pop culture, the net, and politics. Sensation is a kind of bastard love-child of GG Allin and Kurt Vonnegut, a science fiction story that is funny but always discomfiting. I recommend it highly.