Well, it reads faster than Lord of the Rings, as far as trilogies go.
Paul Auster wrote three detective novels that break the traditional standard of what it means to detect, investigate, and deduce; and bundled them up in a "trilogy" that reflects the self as much as it does the urban landscape.
In an age where the best-selling authors are thriller-suspense mystery pop once-a-month bogies (see Evanovich, Clancy, King, Patterson, etc), Auster almost pokes fun at the genre by flipping the proverbial tables on the art of the sleuth. In essence, his detectives are always investigating a case, but in truth, are investigating themselves.
Perhaps the most striking characteristic of the three books is the way Auster plays with names. In the first book alone, the title character Quinn writes under the pseudonym Wilson who has a character named Work and is confused with Auster (a name used in the books which obviously references the author's own self investigation through his characters). In the second book, Ghosts, the characters' names are colors. This fact brings interesting concepts to the proverbial table, which he's already flipped.
There is little that makes these books a trilogy, in the sense that they do not relate to one another (besides vague throw-ins for the faithful Auster reader), but thematically, the books remind us again and again that looking out is just another facet of looking in.