Third Person (Limited Omniscient)
Maybe it's because Go Set a Watchman is an unedited first draft of a first novel, but the narrative voice is inconsistent at best—and sometimes super-duper confusing.
As soon as the train leaves the station, you see something is different in the first paragraph. "She had looked out the dining-car window…" (1.1). "She" is the woman formerly known as Scout—now Jean Louise—and most of the book is told from the outside looking in.
Except, as the book goes on, we end up more and more inside Jean Louise's head, sometimes in the same paragraph as a third-person statement:
She made her way to the sidewalk. Two solid hours and I didn't know where I was. I am so tired. (10.15)
It's jarring, but not as jarring as sometimes slipping into the consciousness of another character, which happens with Aunt Alexandra in Chapter 3:
She could not comprehend the attitudes of young people these days. […] Jean Louise was about to make the worst mistake of her life. (3.71)
Why simply tell us what Alexandra is thinking when Alexandra often says it out loud, or shows it in her behavior? Seriously...we're asking?
You might call it free indirect discourse, but you can also call it confusing.