Rating: 

Author is repeat same task using same clause over and over again.

He using boring words with no insignt to reapeat same thing over and over again.

You can find author is bang on same topic (how to create widget instance to add to the shell) over and over again.

Reader will see author is repeat...do you see some pattern here? I see the same thing happen on this poor written book too.

I'm very disappoint about this book and feel sorry to the author-you spent 300 pages to discuss only one thing: how to create widget instance and add to the shell, aren't you?