It's having trouble parsing the author page because it doesn't seem to be showing the books (the URL shown in the log isn't the exact one that gets used).
Is that actually the correct author page?
This one seems like it might be the actual one, but it doesn't show up in the search unless I search for "Laurence M. Krauss"...
I'll have to add some more error messages to better indicate what that error means.
If the Laurence M. Krauss page is the right one, you should be able to get it working by changing the author to that in the book's metadata.