The following is fairly sobering:
Independent Levee Investigation Team Final Report
The general conclusions of the report can be found here. They fault the hurricane (of course), the performance of the levees (everything from design to operation) and finally how the government functioned at all levels.
At the dinner table and such the eventual fate of New Orleans was something that would from time to time come up for discussion. There was always the inevitable comment that "If a big one comes, New Orleans is history." Of course right now that doesn't seem to be the case as NOLA has returned to roughly 2/3rds of its pre-Katrina size.