Currently when you turn a page, Marvin alternates between showing the name of the book and the name of the author in the title of the page.
Following Shykat's suggestion, I added a "percentage in the book" counter in the title as well. Now the title alternates between book/author/percentage.
You can see what it looks like here: http://marvinapp.com/whatsnew.html
Let me know what you think.