This looks interesting. Louis Van Gaal: The Biography by Maarten Meijer, out in July.

"The question about Manchester United? There is a time and a place. I don't think this is the place. The World Cup is a championship clubs don't take part in, so I am fully focused on the national team. Distraction? It may be a distraction but, for instance, the players - when was it? - on Monday afternoon and Tuesday morning, I gave them some time off, just to get out there. You can't just focus monotonously on the World Cup, so perhaps Manchester United was a good distraction. You can't be fully focused on football for five weeks."