First off, welcome to the asylum, er...Forum!
I don't know of any books specifically on the "Furniture Van". Most books on Panzer IVs have at least a few pages on the Mobelwagen, such as the Schiffer books;
The Panzer IV Family, and
Panzer IV and It's Variants. I have a line drawing, but I haven't found a 4-way one yet.
Here is a preserved Mobelwagen at Saumur;
Additional photos can be seen at; www.jagdtiger.de
Although, beware the other one posted there does not have the correct gun. (a Bofors
)
I wonder if this is the legendary Panzer Gray Mobelwagen of color wartime photo fame, or a Saumur repaint?
And here is a Ardennes paint scheme;