What could be described as the core of Nabokov's brilliance is his ability to create a world and then completely undermine it. I've seen this in the unreliable narrator's of Lolita and Pale fire, in the way they draw you into their irresistible dramas while consistently revealing just how twisted their presentations of the events in question are. I've also seen this in Bend Sinister, in the way Nabokov as author and (for all intents and purposes) god of his character's world peers into the narrative through the odd window of a rain puddle and finally intervenes to grant the protagonist a sort of grace.
Here again in Invitation to a Beheading, Nabokov has placed a fictional being in bizarre and unfortunate circumstances. Here again, in some sense, he seems to swoop in and pull him out of the fire. But, for some reason I can't quite put my finger on, the whole package seems less effective than the above mentioned works. Perhaps both the fire and the swooping are all a bit too bizarre. Here, it's not the narrator's that are unreliable, but the entire substance of the book. The only thing the reader can lean on is the protagonist, a lone candle of sanity in a madly dark and empty world. But is it worth watching him flicker for just over 200 pages to finally see him go all supernova? I don't know. I feel as though something's missing.