I can only attribute the poor ratings for this imaginative documentary to general ignorance on the part of the critics. In fact it is consistently interesting and even moving, if sometimes lacking in continuity, and it tells a compelling story of two brilliant children of a distinguished father, voiced by siblings Vanessa and Corin Redgrave (whose father Michael was no slouch himself). Klaus and Erika Mann were way ahead of Thomas Mann when it came to identifying and combating the Nazi menace.
There are revealing interviews with sister Elizabeth Mann and an old associate of Erika Mann's who performed in the 1930s landmark production of her Peppermill, along with footage of a 60s television interview with Erika, some of her stage and film performances, and recordings of Klaus's voice. Inserted at intervals are re-enactments of incidents from the lives of the Mann siblings and snippets from their works. These are in color and are unobtrusive, though perhaps too fleeting to be wholly coherent. On their own they are well done, however. The music is also stylish and effective. There are plenty of evocative stills and clips from the period, too.
If you are interested in this fascinating and turbulent period and this dynamic family, I recommend this film to you.