You have not violated copyright because things in your memory are not copies. US copyright law defines copies as material objects in which a work is fixed and from which it can be perceived, reproduced, or otherwise communicated, either directly or with the aid of a machine or device.
Your brain is a material object but the the memorized book in your brain cannot be perceived, reproduced, or otherwise communicated directly (I can't look at your brain and "read" the book) and we do not have any machines or devices that can extract a copy of it.
You have not violated copyright because things in your memory are not copies. US copyright law defines copies as material objects in which a work is fixed and from which it can be perceived, reproduced, or otherwise communicated, either directly or with the aid of a machine or device.
Your brain is a material object but the the memorized book in your brain cannot be perceived, reproduced, or otherwise communicated directly (I can't look at your brain and "read" the book) and we do not have any machines or devices that can extract a copy of it.