First identify the structure of each expression, then consider assent separately:
“Book” — a conception.
“Old book” — a qualified conception, not a full assertion.
“This book is old” — an affirmative predication.
“This book is not old” — a negative predication.
Merely hearing the last two does not automatically mean believing them. Assent requires accepting the relevant judgment.
Also, affirmative versus negative and immediate versus inferential answer separate questions.