I hunted this book down after seeing the film that was made of the Ostermann Weekend. At the time, there was 'some' talk of making a movie of 'The Bourne Identity' so having liked the Ostermann Weekend film, I thought I'd get a little bit ahead of the curve by reading the book before the film was made. The Matt Damon film takes the book mainly as 'inspiration', I would say. It truly is an excellent movie and would have made it onto my list of favourite films had I not already burst the ceiling on my 'Ten' favourites. The film managed to re-set the bar in terms of action movies that had already been elevated by films such as 'Die Hard' and 'True Lies', but departs from the book in many, many ways.
One of the most significant, I would suggest, is the main female character 'Marie St Jacques' who was rechristened 'Marie Helene Kreutz' and ably played by Franke Potente in the movie, in the series of books, she is highly capable and intelligent woman who works for the Canadian government as an economist and is a more than able assistant to Jason Bourne throughout his many adventures. She doesn't die in the series of books, but the Marie Kreutz character is killed off at the beginning of the second Bourne movie, which I thought was a great shame.
I stopped reading the Bourne novels after 'The Bourne Supremacy' which unfortunately was Ludlum's last Bourne novel.