What does this 'would' mean?

Question

"I don't know, sir," said Harry.
Snape's lips curled into a sneer.
"Tut, tut -- fame clearly isn't everything."
He ignored Hermione's hand.
"Let's try again. Potter, where would you look if I told you to find me a bezoar?"
Hermione stretched her hand as high into the air as it would go without her leaving her seat, but Harry didn't have the faintest idea what a bezoar was. He tried not to look at Malfoy, Crabbe, and Goyle, who were shaking with laughter.
"I don't know, sir."
"Thought you wouldn't open a book before coming, eh, Potter?"
Harry forced himself to keep looking straight into those cold eyes. He had looked through his books at the Dursleys', but did Snape expect him to remember everything in One Thousand Magical Herbs and Fungi?
(Harry Potter and the Sorcerer's Stone)

It seems ‘would’ mean Potter’s will to read, not for the future possibility. Is this right?

Answer 1

It's equivalent to "You thought you wouldn't bother to read any books before coming" (i.e. - ...thought you wouldn't/didn't need to...).

Snape is gloating over the fact that HP doesn't know what a bezoar is, and taunting him for having been so overconfident that he (HP) thought he didn't need to read/revise before this meeting.

Answer 2

In effect this is a volitive, but it's nothing to do with volitive will.

"I think I will do such-and-such" is a conventional phrase for announcing an intention: think is softer than a flat "I intend to do such-and-such" and leaves room for someone to object or to suggest a better plan.

Thought you would translates this into the 2nd person and backshifts it into the past. Snape implies, sarcastically, that Harry made a deliberate choice not to prepare for the class:

'Ah, Potter, you looked at your book last night and said to yourself "I think I'll skip reading this assignment", eh?'