On Amazon, the book Worlds of honor 6 (which hasn't been released yet), has two "formats" listed, they're both hardback but have different prices, how can I tell what the difference is?
As mentioned in comments, it would seem that the only difference is the date of publication. In this instance, the more expensive "format" has a marginally earlier publish date (14 July, as opposed to 16 July) so maybe these are the first prints hot off the press? Consequently you should probably expect to get it a little bit sooner and have the satisfaction that it is one of the first editions. Some of these early editions may even be numbered?