Joseph Heller mentions in his introduction to the S & S Classics edition of Catch 22 that John Chancellor went around pasting stickers saying "Yossarian Lives" all around NBC studios in New York after having read the book.
One finds this enthusiasm understandable upon first reading of this classic novel (and it is a classic though it is a mess -- which is part of its charm). It is simultaneously funny and tragic, and this material fits naturally with the cinematic talents of Buck Henry and Mike Nichols. They achieve the same tone as Heller's book, but with requisite condensation (even if this film had been twice as long, it wouldn't have been able to capture everything in the book, which is not a condemnation).
The book runs in circles chronologically; so does the film. The book repeats the Catch 22 theme on almost every page (it is certainly the focus of most dialogue); the film isn't as rife with its references but is more explicit when invoking the Catch.
The tragedy of Snowden is a dramatic focal point for both; unfortunately, the film builds it up more (due to its comparative brevity) but falls short in explicating the relevance.
Fortunately the adaptation works incredibly well on several levels. In terms of characterization, Alan Arkin IS Yossarian, Anthony Perkins IS Chaplain Tappman, and Bob Newhart IS Major Major (albeit briefly). The dialogue, which closely follows the novel for the most part, works as well orally as in the written form. And the insanity of war, which underlies all of the book, is well represented.
As a creative work, this film is impossible to divorce from the book, which is difficult to say about many adaptations. As a creation of its own, it suffers some without knowledge of the base material, and as an adaptation of that material it is bound to disappoint fans of the original. There's that Catch again. Viewed with a balance between the two positions (if that's possible), it works extremely well and shows its depth with each viewing in the same way the book does with each reading.
