Nothing wrong with the code you posted..
But make sure that you have stored something in Zend_Registry 'db' (probably done in bootstrap)
And also remove the '?>' from the last line to make sure the problem isn't caused by a trailing whitespace.

What book is it that you are reading?
A good practice, since ZF is so new and still undergoing a lot of changes, would be to cross-reference everything you read with the online docs.
Chances are that whatever is printed in that book is outdated. The same goes for most tutorials that can be found online.