Svejk is not the sort of novel that would appeal to James Joyce, Virginia Woolf or Henry James fans. In many ways it completely disregards ellusive modernity, and deals with things that would have interested Rabelais and Aristophanes: food, drink and sex. Simultaneously its characters find themselves in the butchery of the First World War, and do all they can to get themselves out of it. Hasek is no Remark, and his protagonists are so adept at getting out of the front, that by the (incomplete) end of the book there has still been no actual fighting in it.
Just like Rabelais, Hasek successfully subverts any form of authority. Alhtough Hasek became a communist towards the end of his life, he remained at heart an out-and-out anarchist. Much of his venom is directed at the corrupt and decaying state of Austria-Hungary, but the most choice specimens of it are those reserved for the Church and for religion of all kinds.
Svejk himself is very like Hamlet in one important way: just as it is almost impossible to give a definite answer to whether Hamlet is mad or not, so it is impossible to give a definite answer to the main question surrounding Svejk: is he a patent imbecile or not? In another sense he is much bigger than Hamlet, since he takes over directly the structure of the work, and twists, chops and defines it accordingly. He always tells grotesque stories, supposedly to illustrate a moral of some kind, but these always seem to drift and swerve wildly away, and end up proving nothing at all or something totally different to his avowed aim. They impede the flow of the narrative so much, that by the end there is almost no narrative, just a morrass of subversions, each more hilarious than the one that preceded it.
It definitely is a prime contender for book of the past century.