David Foster Wallace's marginalia-filled self-help books.

Maria Bustillos got access and reports in great detail.

That Wallace even had a copy of Bradshaw On: The Family came as a great surprise to me, as I mentioned earlier. But later I talked with my very old friend, S., who went into recovery almost exactly when Wallace did. S. explained that John Bradshaw was all the rage in AA circles at that time. (Bradshaw is the guy who popularized the idea of the "inner child" in the '90s, and he had a TV show on PBS that was hugely popular.)...

A highlighted passage in Bradshaw On: The Family:

Thought Disorders:
You are always reading about your problems, learning why you are the way you are.
You are numb
You control your emotions and feel shame when you can't
You gauge your behavior by how it looks–by the image you believe you're making.

Lots more at the linked piece, which reads a bit too much like the author's raw notes. The extensive thing ends with this, a quiz Wallace gave to students:

WIN A LUNCH WITH DAVE, SPARKLING CONVERSATIONALIST, WELL-MANNERED EATER, BY SIMPLY IDENTIFYING WHAT ALL THE FOLLOWING WORDS HAVE IN COMMON:

Foreign
Big
Diminutive
Incomprehensible
Untyped
Pulchritude
S-less
Unwritten
Indefinable
Misspelled
Vulgar
High-class
Invisible
Unvowelled
Obscene

Bustillos offers her answer: "My only stab at a guess is that these are words that can be used to describe writing itself, though I feel like 'pulchritude' is kind of wrong, that way. I would love to hear other ideas." No way she'd win the lunch! Isn't it obvious that Wallace was offering up an inkblot to open up the writer's minds? He could then pick the person who'd be most amusing to talk to for an hour. If you just want a correct answer, it's: They're all adjectives. But who wants to eat lunch with someone who'd say that?

ADDED: As several commenters point out, "pulchritude" is a noun. I need to be more careful. At lunch, I would spill the iced tea.