Now all roads lead to France and heavy is the treadOf the living; but the dead returning lightly dance.
Christopher Duffy's Through German Eyes: The British & The Somme 1916, provides another view of the battle.
Peter Hart's "The Somme" is great as well, mostly personal accounts but enough of an operational story to see the battle as a whole. Also, Whitead's "The Somme: Day by Day" is an excellent work that has many maps down to battalion level and briefly describes the action on each day from 1 July through November. Even has the weather for each day as well!