As his initial shock wears off, Ish decides to travel America to investigate whether anything, or anyone, has survived the plague. Travelling east, he gradually finds pockets of humanity, some making ends in this new world, some descending into sedate insanity. But it becomes clear that civilisation is at an end, and Ish returns west to his hometown where, dispassionately, he studies how the natural world responds to the absence of its previously most-fêted offspring. Inbetween his efforts to make a comfortable life for himself, he watches the cyclical rise and fall of populations of animals freed of human control, as well as the gradual fall into disrepair and dysfunction of the human-built world. Unexpectedly, he discovers Em, a woman living nearby, similarly scraping a post-civilisation living. In short order they become a couple, and then a nucleus for a small group of survivors - and their children - to condense around.
As the years pass, Ish begins to grow concerned that all of humanity's learning and knowledge will be lost, and he vainly attempts to spark an interest in the next generation. Instead, Generation Post-Apocalypse gradually adopts less sophisticated, but more sustainable, ways of making a hunter-gather living, while simultaneously receding into superstition and mythology. In time, through triumphs and tragedies, this new way of life prevails as Ish's generation gradually fades away, and Ish himself becomes "the Last American", his memory and awareness dimmed by great age. At the end of his life, Ish comes to accept the passing of the old world he knew and sees the new world as just as transitory. In a moment of clarity, he observes that "Men go and come, but earth abides".
The short answer to the question posed in the opening paragraph is that Earth Abides stacks up extremely well against other novels and films (and videogames!) that tackle the end of civilisation. The above outline doesn't really do justice to the detail that Stewart has invested in his vision for the world. Particularly the effort that he puts into imagining the changes - biological and infrastructural - that follow from the loss of humans. In sending Ish across the country, and in playing out across the full length of his life, Stewart covers the full range of changes, from those that would happen immediately, through to those that would only happen gradually over years.
But leaving aside the breadth and depth of Stewart's playing out of the future, what was more impressive to me was the journey that he sends Ish on. Many end-of-the-world tales conjure up a convincingly human-free future, but few transition to mulling-over the limitations of our lives quite so well. While the narrative at first steers the conventional way that would ordinarily lead to the protagonist rebuilding civilisation, Stewart instead gradually makes the utter enormity of the task facing Ish and Em clear. And unlike similarly-themed novels such as The Road or Oryx and Crake, where hope of civilisation's restoration is wholly (or largely) absent from the narrative, here it's first dangled in front of the reader, before being steadily revealed as an impossible mirage. The future faced by the characters in Earth Abides is a sheer cliff of impersonal difficulty that simply cannot be scaled by them.
Beneath the novel's surface interests in civilisation and ecology, there's clearly more going on. It's difficult to miss the prevalent use of biblical themes and names (the novel's title, for instance), but Stewart also threads the novels with a series of philosophical strands. Some of which I picked up on, some of which only dawned on me when I read the novel's Wikipedia entry! As a more personal aside, I came to interpret Ish's struggle with the future of humanity, and then his acceptance of his passing role in steering it, as being a thinly veiled parable of the struggle that we all face in our own lives. At first, when young, the world seems malleable to us, but as time passes we gradually perceive that its course is far more circumscribed by history, inertia and the opposing wishes of others. Stewart, who was in his 50s when he wrote Earth Abides, was perhaps weaving us more than a simple story to divert us from our daily lives.
The novel does, however, have its, well, quirks. Chief among these are a series of anachronistic slip-ups down somewhat politically-incorrect avenues. For instance, early in the novel, Ish runs into an African-American family eking out a modest existence on a farm. His brief report of their quietly dignified stand against the calamity was possibly quite enlightened for its time in pre-civil rights USA, but it certainly raised my 21st century eyebrows. More troubling is the novel's treatment of the character of Evie, a young woman with either congenital or post-calamity mental health issues. Here the characters come across as the worst sort of eugenicists, at first contemplating euthanasia before finally settling on a pact to categorically prevent her from having children. While one can see the logic in the characters' concerns, they contemplate a semi-Nazi "final solution" for altogether too long to my mind. Such issues often arise in novels from the early- or middle-20th century, and, in context of their times, were probably actually liberal positions, but they certainly give the modern reader pause. Of course, in another 50 years, perhaps some of our forward-thinking attitudes will seem similarly neanderthal (to use what is almost certainly an example of this).
Notwithstanding the preceding, it's difficult not to recommend the novel. It does such a good job of the "empty Earth" trope, that it's a must-read for science fiction fans. And its depths reward readers prepared to wade into them. Though, as I've now spoiled for new readers above, the existential irrelevance of humanity and human lives perhaps makes Earth Abides not for the faint-hearted.