I think this sentence has a comparative adjective: "busier." The superlative form of "busy" is "busiest" (the 'most busy').
busy --> busier --> busiest
A superlative adjective describes something at the upper or lower limit.
Ex. This is the tallest tree on Earth; this is the fastest car I've ever driven; I have the most important job in the company; my house is the best.
(tallest, fastest, most important, best)
In contrast, a comparative adjective compares differences between two things.
Ex. This tree is taller than that one; my car is faster than your car; my job is more important than his; my house is better than my brother's.
(taller, faster, more important, better)
So, adjectives have both comparative and superlative forms:
fast --> faster --> fastest
important --> more important --> most important
Some have irregular forms:
good --> better --> best
bad --> worse --> worst
less --> least
more --> most