Here's a snippet from Comingsoon.net which is quite complimentary to Jason's performance.
There are a couple of movies playing this year that might be seen as derivative due to their genre but feature such good writing and great performances that it's hard not to take them seriously. Viggo Mortensen is getting a lot of attention for the number of movies he's appearing in this fall after his Oscar nomination last year, but the better of his two at TIFF is Good (THINKFilm - Dec. '0, a drama based on the play by C.P. Taylor, about a German literature professor whose fiction novel is embraced by the Third Reich during their early days, allowing him to live luxuriously even as his marriage falls apart. Viggo is very good in this but it's the performance by Jason Isaacs as his long-time friend and colleague, an affluent Jewish scholar whose life crumbles as his friend's star is on the ascendant, that leaves a lasting impression. (And I'm not just saying that because I learned that Isaacs often reads ComingSoon.net!)