I don't know why so many fans & regular readers of Powers are often so down on this book. I thought it was a worthy companion to Last Call, similar in setting but a completely separate novel in it's own right. In this world of ghosts & ghost junkies, the supernatural balance is suddenly rocked by the presence of a great, highly powerful ghost released unwittingly by a teenage boy called Kootie, which he blindly inhales, becoming possessed by it. It is no spoiler to say this ghost is that of Thomas Edison. According to Powers' take on history, Henry Ford contained Edison's last breath on his deathbed inside a glass jar so that he could protect it forever from the fiendish ghost hunters who would be out to get possession of it & ingest it. Over time, Ford was robbed of the jar, and it ended up in the hands of Koot Paraganas' parents, and it was hidden inside a statue of Dante's Inferno. Once the boy releases the ghost in the bottle, this starts the ball rolling for a number of events, as Kootie becomes the object of high rolling ghost hunters, who ingest the ghosts to ultimately not just gain a high, but to gain a twisted sort of immortality. Some of these ghost hunters have been alive so long they have forgotten who they once were, and even how old they are, as the personalities of the ghosts they have greedily inhaled have polluted their very being. (By the way, did you know that ghosts are not just created by death, but when you are born you give off "birth ghost"? Well, you do now).
At the same time, a man called Pete Sullivan is contacted after not hearing anything for several years by his twin sister Sukie, claiming that someone they once worked for is out looking for them. This person is Loretta DeLarava, another ghost junkie who is in fact after the ghost of Pete & Sukie's dead father so she can ingest it. Their father's ghost has just returned from the sea, from inside the belly of a giant, prehistoric fish! So, to avoid being found by this woman, and to protect their father's ghost, they must use a powerful "mask", which is none other than a mummified finger belonging to the great Houdini, along with plaster casts of his hands which Loretta had once stolen from the grave of Houdini, and which Sukie had stolen from Loretta back when working for her.
Anyway, enough about the plot. There is far, far more to it and you are best off just reading it. Typically, real characters are given their own mythos by Powers in this book, and themes & quotes from both Alice in Wonderland & Through the Looking Glass are present throughout the entire story, along with references to Jonah and the Whale, and probably far more things I missed due to not being intelligent enough to pick them up first time through! Personally, I really enjoyed Expiration Date, but as others have said, it probably would not be the best place to start if you are new to Tim Powers. Probably The Anubis Gates would be more accessible to begin with.