It's an eastern european movie at its core: raw, uncompromising, brutal, dim, hopeless and honest.
Brutality actually lead to several people leaving the screening I attended to at Venice 76. Here, this movie was labeled as '14+' but I believe it can be easily rated NC-17. The brutality of this movie includes some very graphic gore (although it's mostly present in the first half of the movie) and sexual-related violence (mostly implied but persistent throughout the film). I believe that, as of on-screen depiction of violence, this film probably outranks Schindler's List (although It isn't as vast scaled as Spielberg's film).
Stylistically, this film uses mostly the visual medium rather than conversations to provide information to the viewer. Dialogue becomes secondary at a point where the main character maybe utters a couple of lines throughout the movie, and some of the characters he meets with are entirely silent (Skasgard's character, for example).
The film has a very precise structure: it is made up of 8 chapters, each entitled after a character that the kid meets with, and each chapter reaches a moment when the screen fades to black. After that, a sort-of connective sequence displays the events that lead the kid to change his whereabouts. Among the characters he meets, the audience might recognize Alexander Skasgard, but also Harvey Keitel (in an entirely czech-speaking role) as well as Barry Pepper and german actor Udo Kier.
I wouldn't say that The Painted Bird is a holocaust or ww2 movie, or better, it isn't only that. Thematic elements that relate to either the Holocaust or the War, with the exception of a german plane seen early on, come up only after around one hour in-movie. Before that, whatever happens is mostly related to a strongly rural and superstitious society.
The Painted Bird pays implicit homage to several Eastern European films. The opening sequence mimics the one seen in Jan Nemec's "Diamonds of the Night", a lot of settings remind Elem Klimov's "Come and See" and Tarkovsky's "Ivan's Childhood", the overall fatalist tone reminds strongly of Bela Tarr's films.
It is an outstanding accomplishment, and I sincerely hope that this movie, despite its graphic content, receives enough recognition.