It's still available a few places used and new. You can check this link to my Hollywood Series page, with a link to books still available in the US. I found it in two different releases from 1983 from Alfred a Knopf. The used ones maybe mixed.
In the UK? There are a variety of books still available to buy new and used. Check your used local bookstore too.
If you are on a budget or just want to see the book before buying, you can always check it out at your local library. It's available worldwide. Here's a link to World Cat for libraries it is located.
Still tickets available for the event at Royal Festival Hall, but going fast.
Also, here's an article from Sense of Cinema from 2006, on the background of the different versions.
Update: Click this link more posts on NAPOLEON.