This part of the novel comes towards the beginning and shows us what Montag's job was and presents us with a world where books are considered illegal and burnt as a result. However, what is surprising about this is the way that Montag acts, seemingly in an involuntary fashion, by stealing one of the books he finds in the old woman's attic and not destroying it as he should. Note how this is presented in the text:
Montag had done nothing. His hand had done it all, his hand, with a brain of its own, with a conscience and a curiosity in each trembling finger, had turned thief. Now it plunged the book back under his arm, pressed it tight to sweating armpit, rushed out empty, with a magician's flourish! Look here! Innocent! Look!
So, Montag steals a book that should be destroyed in the old woman's attic--an act of rebellion which is very dangerous. However, you need to note the way that this act of stealing introduces a motif in the novel. Montag's hands again and again are shown to act in an involuntary fashion, seemingly independent of Montag's own desires, thoughts and wishes, and this is the first instance of this motif. You would do well to identify other examples and consider how this shows the deeply divided self of Montag.