Which tense when talking about books?

Which tense should you use when talking about a book if it is narrated in both the past and present tenses? I am asking this because in To Kill a Mockingbird (Can you underline book titles here?) Scout uses both the present and past tenses when narrating the story.

When analyzing literature, it needs to be done in the present tense. Literature lives as you read; it never happened, it is always happening.

Pretend this is part of an essay

For example, when "Dill [leaves them] early in September... [they see] him off on the five o'clock bus."

In your writing about a book, I think you should select either present tense or past tense and stick with it throughout your report. So, for example, you might say:

In this coming of age book, Scout finds that rumors have destroyed Boo Radley's reputation. OR, In this coming of age book, Scout found that rumors had destroyed Boo Radley's reputation.

We call this being parallel, or staying true to your writing's tense.