What is the climax of the book On the Road?
If we see this book as being centrally a story of the friendship between Sal and Dean and the way that they journey together, both physically and in other ways, then undoubtedly the climax of that story is the way in which that friendship and their road trip ends at the same point when Dean basically abandons Sal to pursue his own needs and desires.
Let us remember that this occurs in Mexico City, where we can see that Sal, Dean and Stan revel in the frantic and busy setting and really enjoy everything they experience. Sal at this stage becomes very sick with dysentry, but it is precisely at this stage that Dean decides to leave him in Mexico City, a strange and foreign country, because he feels he wants to return to Inez in New York. This is the climax of the story because it effectively marks the end of their friendship and their journeying together.