Calculate the required increment

To make the number of non-fiction books equal to fiction books, the increase needed is the difference between the two counts.

$55 - 22 = 33$

Set up the percentage increase formula

We need to find what percentage 33 is of the original number of non-fiction books (22).

$\text{Percentage Increase} = \frac{33}{22} \times 100\%$

Perform the final calculation

Simplify the fraction $\frac{33}{22}$ by dividing by 11, which gives $\frac{3}{2}$, and then multiply by 100.

$\frac{3}{2} \times 100 = 1.5 \times 100 = 150\%$