I wouldn't have believed, before reading Catch-22, how derivative MASH and other war comedies are, in every medium. The ideas no longer seem new, but they're delivered in so riveting a manner that it doesn't matter that they've been ripped off a thousand different ways.
Catch-22 follows the adventures of Yossarian, a bombadier, and his cohort of flying bombers on the island of Pianosa near the end of World War II. Yossarian is either the only sane person in his unit or the only crazy person, depending on who's doing the talking. For example, he insists that everyone is trying to kill him. He starts out in the hospital, with a fake liver complaint that's keeping him on the ground and away from enemy flack. The book ends with him in the hospital again, with a genuine injury. In between the narative meanders in time and space serving up biting satire of military bureaucracy, the wartime mentality, and the general blindness of the human condition.
Yossarian is intent on preserving his life, a fact which does not endear him to his superior officers. He's also a crack bombadier. But fear has infected him and made it impossible for him to function 'normally' - as normal as normal goes on an island inhabited solely by men torn from their familes and loved ones, periodically dropping bombs on strangers who try to kill them back. Yossarian tries everything he can think of to escape flying more missions, but each path in sequence closes to him. Gradually, as the book goes on, he loses his hope and his friends. He only manages to cling to his survival instinct and his integrity.
The reader is wrenched from one day to the next (or previous) without mercy. Yossarian's moment of horror, helping Snowden die over Avignon, pops eerily onto the scene at odd moments. Dreamlike repetitions and confusions lend it all an eery quality of (dare I say it?) deja-vu, punctuated by grisly horrors and absurd comedic moments. There seem to be strong implications that the entire novel is actually taking place in Yossarian's mind as a kind of combination flashback/fever dream.