Because brains are very delicate, always handle them with care; they have a tendency to fall apart.This quotation comes from page 732 (in my copy) of the best-selling American book within what genre? My parents' edition of the book also contains instructions relating to squirrels.
BONUS: What fictional pirate could be fittingly added to this puzzle?
The fictional pirate is Long John Silver (not Blackbeard, who was a real person).
Solution
From top to bottom, left to right: William of Orange, John Green, P!nk, E. B. White, Jack Black, Violet Beauregarde, Erik the Red, John Brown, and Henry Gray (namesake of Gray's Anatomy, not to be confused with Grey's Anatomy).
Congratulations to yesterday's partial solvers Inca, Josh Moore, Maddy and her mom (who got the bonus), Connor, and Graham, and complete solver Jason. Thanks to everybody who made a guess!
Ten years later, Dr. Shapiro revived Puzzle of the Day at Proof School, writing each day's puzzle on a name tag. After 600 puzzles or so, he was just starting to feel normal about students reading his chest all the time when campus closed and the puzzle, like the rest of our lives, moved online. New puzzles are posted daily on school days.
Want to catch up on old PotDs? There's an archive currently containing puzzles from March 2020 to March 2021.