curlingstraight: Ignore the others, they don't know what they are talking about
There isn't an easy way to do this at the moment. Deleting and resending the books is it. But, you can use the Kobo Utilities plugin to store the reading status and restore it after you resend the books.
I have been asked to consider this problem. The original reason was to have an easy way to move books to the SD card from the main memory. But, when/if I do it, I will make it a more general function to rearrange the files.