This book seems the product of a restless mind.
I was expecting (or hoping) it would be more interesting to me, but alas, it was only average. I was thinking as I read Stardust why the story didn't excite or interest me more, and I came up with several issues:
1) The format of fairy tale works against the novel form and length. Fairy tales are usually quite brief, which is a good thing. They do a very poor job of developing characters beyond the most basic stereotypes and have no issue with introducing new characters throughout the story. When you lengthen the story to 250 pages, however, this becomes a problem.
2) The narrator's voice intrudes. It felt forced to me. Too cutesy.
3) Tone. There is an odd tone of chaste innocence (inherent in the fairy tale form) married to adult levels of violence and sexuality. This is a story precocious kids might pick up because of its fairy tale format, but there are situations that young children ought not read.
4) A lackluster central love story. It's the love story that ought to tie everything together here -- the gradual change in the relationship of Tristan and Yvaine -- but there is so little emotional depth, it means virtually nothing to the reader. I get that Gaiman wants to move out of the "happily ever after" territory, but it's almost as if he is purposefully avoiding or deriding the idea of a loving couple.
5) Derivative on every level. I wrote a few reviews ago that a good book steals its ideas and does it so well and makes such clever use of them that the reader doesn't seem to mind. Well, with Stardust, the skill was lacking and theft was more obvious.
6) The addition I read had an author's intro and postscript that felt really smug and self-congratulatory. "I sat down with my fountain pen and paper and began to write." Gaiman is fantastically adept at self-promotion. He needs to work more on the written product.
A book ought to reward in proportion to its length, as readers commit those scarcest of life's resources, time and attention, to its pages. Stardust offers enough pleasure to fill a fun novella of 50-100 pages, but little more. Perhaps Gaiman and his publisher had a novel in mind in order to provide for that other resource we always seem interested in: money.