Comparison to the book
Just finished reading the book "Thank You For Smoking".
In short: the book has a better start, but falters towards the end. The film has a better ending.
The long version...
Jason Reitman has done a smashing good job with the movie script. He follows the spirit of Buckley's book closely and many passages are lifted directly to the screen. The addition of Joey in the film (he only has a minor part in the book) was a good move by Reitman because he becomes the proxy for us viewers, which gives us great insight into Nick's work.
Reitman also did a good job in weeding out some of the more ludicrous passages, such as the real culprit and motive behind the kidnapping, and its eventual resolution. Spoiler follows...
Turns out BR and his secretary ordered it, then they framed Nick for it through a really convoluted plan involving sex in the dark, rubber gloves and other such nonsense. BR also had a murder squad(!) working for him and the MOD Squad manages to turn it against him.
In the end all of the MOD Squadders find new jobs and actively turn against their former employees in a wishy-washy goody-two-shoes ending.
The book starts good and much of what we see in the film is desribed more detailed and with meatier dialogs on paper. But after the kidnapping the book jumps the shark and the resolution is short and rather unsatisfying. Buckley keeps us in the dark and dances around the issue like a tease without revaling anything at all until the very end... and then resolves everything in just a few pages.
In my opinion: get the book, read everything up to the kidnapping... then see the last half of the movie again.
/J