The Long Fall is clearly meant to be the first of a book in a series, and I gather that Leonid McGill has been fleshed out after first appearing in a supporting role in some of Mr. McGill's earlier work. As a result, I'm not exactly sure how many of the people in The Long Fall have previously appeared in other Mosley novels, but regardless, the sizable number of intriguing characters in the book really add color and richness to the world that McGill inhabits. Given the fact that the actual plot of The Long Fall isn't all that groundbreaking (striving to keep true to traditional noir storyline as opposed to trying to break new ground), an interest in the characters themselves becomes that much more important.
Fortunately, Mosley is adept at breathing life into characters and making you care about them. His central figures have ambiguities, nuances, and quirks that make them much more than the stereotypical noir figures that might have taken shape in lesser hands, and Mosley manages to infuse a great deal of vibrancy into the more "minor" supporting characters as they move alongside the major ones, even when giving us only small glimpses into their lives.
Anyway, I liked The Long Fall. I recommend it, especially if you're into detective books and/or noir. It's a book which feels thoroughly contemporary while holding true to the stylings of traditional noir, and it's a quality addition to the genre- a good read, with characters and stories that sucked me in and pulled me along.