Fall of Giants by Ken Follett

The first in a planned trilogy, Fall of Giants (and one of the giants is the size of this tome!)  follows five families from the mines in Wales, to Lenin's iron grip in Russia.  I thought at first that there were too many characters to remember, but that isn't the case.  As the stories unfold, each character manages to imprint him/herself on one's memory, so even if you can't get back to the book for several days, there won't be a problem getting back into the story.
World War I strains each of the five families, and their lives overlap, though some are working class and some are upper crust, even royal.  One of the most fascinating things about this book is the contrast in living conditions and expectations of the different classes.  Recommended!