Rated as literature, this would be a three. I rated it a four due to the timeliness and resonance of the themes for today's news. It is set in the 1930's amidst Depression, Prohibition, robber baron capitalism, and a culture of acceptance of spiritualism (use of mediums and seances to communicate with the dead), anti semitism, and racism.
I learned things about the period. Did you know that in the 1920's there was a very large and open KKK group in Long Island New York, holding rallies? Henry Ford was writing anti-semitic screeds and publishing them in the Dearborn newspaper and distributing them in all the Ford dealerships. He also re published as fact the racist conspiracy theory forgery Protocols of the Elders of Zion, and distributed half a million copies. He and a number of the other wealthy capitalists believed in white supremacy in the genetic sense and in eugenics, a plan to purify Aryan blood through "scientific" breeding plans.
Henry Ford helped inspire Hitler and was the only American mentioned in Mein Kampf. On Ford's 75th birthday, Hitler awarded Ford the highest civilian medal of Nazi German. The Protocol of the Elders posits a cabal of rich Jews who are secretly plotting to take over the world. Jewish bankers would take over and control the world economies, Jews would take over and control the press, and ultimately they would destroy civilization-as-we-know-it. Hitler relied on the Protocols as justification for his persecution of Jews and quoted extensively from it in Mein Kampf.
As is obvious, the QANON conspiracy theory is The Protocols of the Elders warmed over and made even more stupid. Trump and Trumpist Republicans have been promoting QANON ideas and people. Trump also believes that he has superior genes, that the fact that he has an uncle who is a MIT professor means that he (DJT) is at least equally smart and knows things intuitively without having to study. This year Trump visited Ford Motor Co and praised Henry Ford, noting that he has "good bloodlines."
So back to the book. The book refers to the racism, anti semitism and spiritualism of the times and specifically to Ford. It educated me on some things I didn't know. Best the end it brings the theme forward referring to this strain of racist, white supremacist thought as The Monster and predicting that it would keep re-emerging. (The book was published in 2004, well before Trump.). So it had strong resonance for me.
As literature, not so great. It is a murder mystery where the "detective" trying to solve the case is a young con artist in training. He and his mentor are fake mediums taking advantage of gullible, rich spiritualists. He has a team of carnie side show people to help him, literally the most motley crew ever assembled. There are a couple of romances, but none of the women come alive as real people. In the way of a certain genre of murder mystery, the bodies start proliferating, it gets gorier and gorier. There is a bloody climactic scene where our hero and the motley crew kill seven bad guys in various creatively gruesome ways.
So recommended for the history, but the history is mostly backdrop and the rest is a just so so book.