It's more than a cover.  It's a book cover of a book cover with a portal to another world. 

Many of its images refer to important symbols in the story.  A broken snowflake pendant . . . a glittering white butterfly . . . the book itself . . . and its revealing window with the glowing dwarf evergreen and purple door.  Where does it lead?  Did you notice the freaky horse in the upper right corner?  It's from a famous painting*—and one of the story's more "charming" characters.  

 

How are they all connected?

 

 

Cover Design by Tango Communications

 

 

*The Nightmare,  Henry Fuseli (1741–1845). 

 

This work of art depicted in part on the cover is in the public domain in the United States, and those countries with a copyright term of life of the author plus 100 years or less.  This file has been identified as being free of known restrictions under copyright law, including all related and neighboring rights.  The image and reproduction thereof are in the public domain worldwide.  The reproduction is part of a collection of reproductions compiled by The Yorck Project. The compilation copyright is held by Zenodot Verlagsgesellschaft mbH and licensed under the GNU Free Documentation License.