Hard to read

If someone is 'hard to read,' it means that is hard to anticipate what they are thinking or feeling.

Example:
-Do you think your mother-in-law liked your gift?
-I don't know. She's really hard to read.

Between a rock and a hard place

If you're 'between a rock and a hard place,' it means you're in a difficult situation with no good way out. No matter what you decide to do, there will be negative consequences to your actions.

Example:
-I can buy groceries and pay my bills this month, or I can refill my prescriptions.
-You're definitely between a rock and a hard place.