What are the sirens of titan?

What was the significance of the sirens in The Sirens of Titan?

• The Sirens, are of course, the luminous, beautiful sirens at Titan. Yet, they play little to no role in the actual book itself. Why did Vonnegut choose to name the book after mystical characters that end up playing no role in the book?

• Answer:

  I haven't read TSoT recently and don't have a copy handy, but I would say the sirens play a very important role as illusory bait which motivates much of the book's action. The fact that they turn out not to be what they seemed (or were hopefully imagined to be) at first is typical of Vonnegut--he pulls the rug out from under his character to comment on the folly of desire (we chase chimeras or desire things which in the end don't really satisfy). The sirens are fit for the title because the novel as a whole is concerned with purposes and motives. Individuals in the book assume they're fated to do important, meaningful work but in the end it turns out all humanity exists only to provide a spare part for a spaceship. The hollowness of illusion returns in a minor episode in God Bless You, Mr. Rosewater where a character is chided for leering at images in a girly magazine, which he is reminded "is just paper."