For the German perspectives, I would suggest:
'The Mons Myth: A Reassessment of the Battle' by Terence Zuber - a reasonable review of the German aspect of these battles but his conclusions must be treated with caution and his assessment of the BEF is woeful.
'Le Cateau' by Jack Sheldon and Nigel Cave - part of the Battleground Europe series and provides more material from a German perspective.
'The Battle of Mons: The Official German History' by Holger Puttkammer and me. This is a translation of Die Schlacht bei Mons, which was released in 1919 by the German Great General Staff. It is the definitive German account of this battle.
Robert