Why the green book matters

A Practical Guide to Quantitative Finance Interviews by Xinfeng Zhou — the "green book" — is the canonical quant interview prep text. It's not perfect (some solutions are terse, some problems are outdated), but it's the closest thing the industry has to a standard.

Why it works

• Breadth: covers brain teasers, calculus, probability, stochastic calculus, options, algorithms, numerical methods. Most interview topics in one book.
• Difficulty: problems are realistic — not trivial, not absurd. Right level for actual interviews.
• Concise solutions: you can review quickly without drowning.

What it doesn't cover

• Modern machine learning (very limited).
• Coding interviews (only basic algorithms).
• Markets intuition (assumes you've read Hull).
• Behavioral questions.

How to use it

• Do every problem. Don't skip "easy" ones — they show up in interviews.
• Time yourself.
• After solving, read the book's solution even if yours worked — there's often a faster way.

That's exactly what this site helps with: daily problem-unlock streaks, AI hints when you're stuck, a reasoning workspace for the open-ended ones.