Earlier this week I posted a review here of Justine Larbalestier's wonderful new book Liar which had a bit of cover controversy because the book was slated to be released in the USA with a white model on the cover--despite the main character being very obviously black. I also received a wonderful comment on that post asking how such things could happen and if authors have approval on their covers.
The short answer is sometimes they do, but not always.
There is a lot of really information out in the world from authors, readers, and bloggers about book covers. Too much information, really, to put into a comment as I had initially planned. Which is why you get this post.
Onward to the information and sources:
Sometimes authors do get input on their covers and it leads to cool ones like that found on Barry Lyga's Goth Girl Rising (cover discussed here on Melissa Walker's blog: http://www.melissacwalker.com/blog/2009/10/cover_stories_goth_girl_rising.html)
Other times it results in inaccurate covers like the one found on Liar which Justine Larbalestier discusses at length, and more eloquently, than I ever could in a series of posts on her blog, particularly in this post: http://justinelarbalestier.com/blog/2009/07/23/aint-that-a-shame/
If you interested in hearing about more book covers, Walker also has a lot of posts where other authors discuss their covers here: http://www.melissacwalker.com/mt/mt-search.cgi?IncludeBlogs=1&search=cover+stories
Maureen Johnson has also discussed her covers briefly on her blog:
Johnson's posts also led me to Bookburger's commentary on the crazy cropping that goes on in a lot of covers (including several of Johnson's): http://bookburger.typepad.com/bookburger/2007/01/covergirl_repor.html
Bookburger has a whole feature of cover reviews found here: http://bookburger.typepad.com/bookburger/covergirl/
If you'd like to see some behind-the-scenes shots of what it takes to shoot the photos for a book cover you can check out Ally Carter's post about the cover of her upcoming book Heist Society here: http://www.allycarter.com/labels/Covers.html
Laura Schaefer's blog has a post with shots of the cover shoot for The Teashop Girls (which I think has a perfect cover that totally nails everything about the book) on her blog here: http://teashopgirl.blogspot.com/2009/03/delicious-behind-scenes-look-at-teashop.html
"Cover twins" are another interesting phenomenon in the world of book covers which happens when two covers use the same stock photo as happened with North of Beautiful by Justina Chen Headley and Evermore by Alyson Noel. Their specific "twin-ness" is discussed here: http://www.publishersweekly.com/article/CA6646736.html?nid=2788
Finally, if you are interested about book covers in general, you should check out JacketWhys, a blog all about children's and young adult book covers as well as having a handy page linking to articles and other information on cover design found here: http://jacketwhys.wordpress.com/articles/. The site was inspired by The Book Design Review which discusses cover design for a broader spectrum of books.
Hopefully all of that will answer some questions people were having about book cover design or at least provide some more information on the subject.
If you have any other sources readers should know about be sure to post it in comments!