SecretBook

It's free, but the problem is, as far as I can see, there is no documentation. I'd love to give it a try, but it seems people who are brilliant at writing programs, haven't the first idea of what it's like for us mere mortals, to understand how to use their creations. Or is it just me?
Version 3 is free if you access it through the Macworld DVD and works with Tiger. Version 4 ($25) works with Leopard and can Sync with the iPhone and Touch.
Has anybody else used this software, or have any views on it? It can be found at:
http://bookshelfapps.com/secretbook.ph