How perfect is Voynichese?

[ololololo]

For a letter-size document, perhaps.  A book-size text in codebook cipher can be cracked by guessing the most common words and using external clues (topic, illustrations, recurring formulas, partially leaked plaintext...) 

This is possible, but if the text has been distorted in an unknown way (at least the words may have been separated, but we may be missing something)... unlikely