* Scope and Depth: Prep books often include more challenging problems than you'll see on the actual SAT Subject Test. They aim to prepare you for the hardest possible questions, ensuring you're ready for anything. The actual test might have a wider range of difficulty but fewer extremely difficult questions.
* Question Style: The style of questions in the prep book might differ slightly from the actual test. This can make the prep book feel harder, even if the underlying concepts are the same.
* Focus on Difficult Concepts: Prep books tend to emphasize the trickier concepts and often include fewer practice questions on the easier topics. This creates a skewed perception of difficulty.
In short, while the McGraw Hill book likely covers the material comprehensively and includes challenging problems, it's probably not representative of the *exact* difficulty level you'll encounter on test day. Consider it a rigorous training ground, aiming for mastery rather than a perfect simulation of the test's specific difficulty. Using multiple resources and practice tests will give you a better overall sense of what to expect.