Nature as the Antagonist:
* The Call of the Wild by Jack London: Buck, a dog, struggles against the harsh realities of the Klondike Gold Rush.
* The Old Man and the Sea by Ernest Hemingway: An aging fisherman battles a giant marlin and the forces of nature.
* Into the Wild by Jon Krakauer: A young man's struggle against the unforgiving Alaskan wilderness.
* Life of Pi by Yann Martel: Pi Patel's survival at sea is a battle against the elements and the ocean's dangers.
Societal/Political Systems as the Antagonist:
* To Kill a Mockingbird by Harper Lee: Scout Finch and her father navigate the complexities and injustices of the Jim Crow South.
* 1984 by George Orwell: Winston Smith rebels against the oppressive totalitarian regime of Oceania.
* The Grapes of Wrath by John Steinbeck: The Joad family struggles against the economic hardship and social injustice of the Dust Bowl era.
* The Handmaid's Tale by Margaret Atwood: Offred resists the totalitarian theocracy of Gilead.
Internal Circumstances/Personal Challenges as the Antagonist:
While often categorized as "man vs. self," these can also strongly involve external circumstances which exacerbate the internal struggle:
* A Farewell to Arms by Ernest Hemingway: Frederic Henry confronts the horrors of war and the challenges of love and loss.
* The Kite Runner by Khaled Hosseini: Amir grapples with guilt and redemption against the backdrop of war-torn Afghanistan.
* The Count of Monte Cristo by Alexandre Dumas: Edmond Dantes's quest for revenge is fueled by the unjust circumstances that led to his imprisonment.
This is not an exhaustive list, and many books blend multiple types of "man vs. circumstances" conflict. The key is that the protagonist faces obstacles outside of their direct control, requiring resilience, adaptability, and often a change in perspective to overcome.