Also note these central disagreements between specific books:

Homer (The Iliad) versus Remarque (All Quiet on the Western Front): Is martial glory possible, or is modern war fundamentally dehumanizing?

Sun Tzu (The Art of War) versus Clausewitz (On War): Is supreme strategy about avoiding costly battle, or understanding battle as an instrument of politics?

Thucydides (History of the Peloponnesian War) versus Tolstoy (War and Peace): Can we explain wars through power and state interests, or are historical events too complex for such explanations?

Bhagavad Gita versus All Quiet on the Western Front: Can participation in war constitute moral duty, or does war destroy the very moral world that gives duty meaning?

The Aeneid versus The Trojan Women: War seen by the founder/victor versus war experienced by the defeated

Henry V versus Don Quixote: The construction of martial heroism versus the dismantling of martial mythology

Machiavelli (The Prince) versus Marcus Aurelius (Meditations): Political necessity and force versus virtue and self-command

Clausewitz (On War) versus Hersey (Hiroshima): War as a rational political instrument versus technology that makes its consequences potentially catastrophic  

Herodotus (The Histories) versus Ibn Khaldun (Muqaddimah): How ambition, empire, cohesion, prosperity and decline produce cycles of conflict

Thucydides (History of the Peloponnesian War) versus George Orwell (Homage to Catalonia): How war corrupts language, truth, political institutions, and moral standards

One can see the differences – war as duty, war as strategy, war as politics, war as glory and war as human catastrophe.