This should be a blockbuster. I don't understand why it isn't doing better business. It's quite well done, a bunch of fun, and a more compelling story than many more successful critical busts like Transformers 2 and 3.
It's been a while since I read the book on which this based, so I can't really tell where the details might vary from the original story. If it does, it's not by much. They major characters and plot points are there. I was afraid from the previews that it would all be CGI with a few live actors. But there were many live actors and the CGI was very well done. The acting (both live and animated) worked for me. The spectacle was spectacular. There is even some substance involving the meaning of honor.
John Carter (IMDb)