Well, I realised after posting that my comment was a little harsh/in-constructive.
The code behind it is poor, but that's me as a web developer looking at it.
The main thing is usability really.
Splash page
Always a bad idea.
Imagine you wanted to go to Tesco and you get to the door and they make you do something before you go in. That's gonna piss you off, maybe not a lot, but it's still an extra unnecessary thing to do to before you get in. A splash page does that. I get to a website and I wanna see it, I don't want to have to click another time before I can get to the content.
The videos page
I have to click back to get to the videos menu to watch a new clip. Why not have a list of thumbnails under the Youtube video that link to all the other videos in that category?
My current user journey is:
Splash page > Home page > Videos page > Category page > Video > Category page > Video
That could easily become:
Home page > Videos page > Category page > Video > Video
Buying the book
There is currently only one link to buy the book, which is sat in with a load of other similarly styled links. Why not have several 'calls to action' on each page? A banner above the Youtube video that says 'Buy now!' and attracts the user, a smaller banner under the links in the right hand column here? A banner just under the foreword copy?
Currently you're only giving users one link to use to spend money with you, put links everywhere, make them stand out, lead the user on a buying journey…
Hope that is more insightful (I won't comment on the code (unless you really want me to…))
Harry