There's a tendency in these sort of works to present the protagonists as some sort of magical Bugs Bunny or Coyote-like tricksters who never face the real problems someone blowing up bridges and draining the oil from construction machinery would be likely to face. But that's not how they're presented here.
Instead, these people have all the trials and tribulations you'd expect of four amateur saboteurs trying to cut fences, blow up bridges, and destroy coal plants. They worry about each other, whether they'll go through with the plans or whether one of them's an agent provocateur. Sometimes they try to blow something up, and it doesn't blow up. When they do succeed in blowing something up, the story doesn't stop and move on to the next target. Instead they often face the very real problem of exactly how you get away from the middle of nowhere when there's only one road between you and anywhere, and the authorities are coming at you down that road from both directions. A lesser book would ignore such a difficulty.
They try to avoid taking human life, but find that an extremely difficult ideal to adhere to in the face of pursuers toting shotguns. They frequently come within inches of getting caught, but if they do escape, the escapes are plausible. In short, these people face the likely consequences of their actions. You really feel that if four people did get together to blow up bridges, this is very close to what their story might truly be.
And let's talk about those four people. My own fiction has the annoying habit of having only one voice, mine. And every character I write tends to become me. This isn't an unusual problem in mediocre fiction. But Abbey's drawn four very distinct characters each with obvious personalities. The characters are presented so vividly, accurately, and consistently that by the end of the book you can read a long section of dialog and always know who's saying what without explicit cues. Bad novels, especially bad political novels, have a tendency to draw flat, indistinguishable characters, prone to excessive speechifying. (cf. Atlas Shrugged) Abbey's avoided that trap, and created four people you really grow to care about.