It's captivating to learn about the events that were said to inspire 'Citizen Kane'. 'Mank', which tells the story of screenwriter Herman J. Mankiewicz, makes for an enjoyable viewing experience. There’s a great deal happening and most of it is engaging, though familiarity with the 1941 movie would certainly help. I appreciated that they chose to present events in a non-chronological order and in black-and-white, mirroring the style of films from '41. The performances are noteworthy. Gary Oldman as Herman is remarkable; I thought he occasionally leaned toward overacting—as did Amanda Seyfried portraying Marion, though only for brief moments. Overall, both deliver excellent work. Arliss Howard (Mayer), Lily Collins (Rita), and several other actors also contribute positively to the film.

Source on TMDB