A serene atmosphere is a must for writers.
Substitute 'peace and quiet' as an entity in place of 'serene' and:
Peace and quiet is a must for writers.
We are lumping the two together as a 'state' of our surroundings.
But similarly, we could regard the two terms individually:
Mr. Ishac acknowledged that peace and quiet are relative concepts in New York
For many people it seems peace and quiet are a luxury
Peace and quiet are apparently essential to some patients' recovery
Peace and quiet are at a premium in our hectic world.