I recommend visiting www.salience.nl (unfortunately you will need to have flash installed) if you are interested in courses, though you requested books/websites only.
They are very specialized in XML and give customized or general XML trainings/courses (from theory through to tools etc.) in the Netherlands (in Dutch!) so I'm sure they can help you out. I know they have given trainings specifically to publishers before, which might be of further interest to you (ie: SGML vs./to XML).
I used to work there... if you contact them say hi for me!
From: Baudoncq Gert [mailto:Gert.Baudoncq@zeno.be]
Sent: Friday, May 18, 2001 12:14 PM
To: 'Amanda Woestenburg'; xml-chat
Subject: RE: get started