Final answer:
Montag conceals the books to seek knowledge and rebel against a society that suppresses critical thinking.
Step-by-step explanation:
The main reason for Montag concealing the books in Ray Bradbury's Fahrenheit 451 is his growing dissatisfaction with the society in which he lives, where books are banned and critical thinking is discouraged. Montag conceals the books because he is starting to question the world around him and seeks knowledge and depth that his society has suppressed.
Though he is not entirely sure of his motivations at first, it becomes clear that Montag's actions are a rebellion against the anti-intellectual and oppressive nature of his government and culture.