Meaning of "She is an open book in her own cipher" [closed]
An Open Book
Merriam-Webster defines this as
a person or thing that is easy to learn about and understand
Cipher
M-W defines a cipher as:
2b: a message in code
The sentence is an oxymoron. It probably means that she should be easy to understand, but you can only understand her life through her cipher, making her difficult to decipher and understand.