I have a project with a root directory of E:\inetpub\wwwroot\stuff. I have additional directories set to E:\inetpub\wwwroot\books. From a page in the stuff directory I'm trying to execute the following:

header("../books/login.php");
die();

This results in a blank page. Control does not transfer to the ../books/login.php page. What am I doing wrong?

hmm, your script is not producing any output, except header. So the page in the browser, if you open it in a browser, is expected to be blank.
If your intent to get web browser redirected to another page and send next request to login.php, you probably want to say that this login.php is new location and provide correct URI for that.
Header function is a generic header producer. For instance it can send 404 status, like header("HTTP/1.0 404 Not Found"); and can't guess for you that what you have there is new location. If location is what you need, say so: header("Location: ../books/login.php", true, 302);

Thanks. That was the problem.