I quite like Joseph Conrad but I didn't know he ever collaborated with anyone, let alone Ford Madox Ford and still less on a quasi-SF/ Fantasy novel.
The Inheritors (1901) by Joseph Conrad & Ford Madox Hueffer
http://www.amazon.com/dp/B0084BCMX0/
http://www.amazon.co.uk/dp/B0084BCMX0/
http://www.amazon.ca/dp/B0084BCMX0/
It looks at society's mental evolution and what is gained and lost in the process. Written before the first World War, its themes of corruption and the effect of the 20th Century on British aristocracy appeared to predict history.
http://en.wikipedia.org/wiki/The_Inh..._Madox_Ford%29
Also
Romance by Ford Madox Ford and Joseph Conrad
http://en.wikipedia.org/wiki/Romance_%28novel%29
http://www.amazon.com/dp/B004UKB3LQ/
http://www.amazon.co.uk/dp/B004UKB3LQ/
http://www.amazon.ca/dp/B004UKB3LQ/
They also collaborated on _Seraphina_ but it doesn't seem to be available.