When is a book really updated? Data cached?

I love the easy it is sending books to the reader via dropbox. :)

But, I have noticed that if I do an update to the epub and put the new one in dropbox, it stills seems to be the old one on the reader.

At least it looks like it.

Before I go down the path of doing a bunch of test to try to figure out what happens when, I'm sure others have done the same thing before me. Is there any writeup about this? Or any details about books.db?


For example:

I put the epub in dropbox, sync on the reader and open the book. I delete the book on the reader, sync, and it removes from dropbox. I change something in css, or add an <p>-line, put the updated epub in dropbox, sync on the ereader, open it. It does not show the new changes.

Is the books cached? And not cleared even when deleted?