This is the 8236th most frequent Russian word.
маленькая
Small; little.
'Маленькую' is used as an adjective in its accusative form due to the direct object 'книжку', specifying the book's diminutive size.
Вы видели ту маленькую книжку на столе?
Did you see that little book on the table?
In this sentence, 'маленькая' is used as an adjective to describe the noun 'собака', indicating its size.
Маленькая собака сидит под столом.
The small dog is sitting under the table.
Here, 'маленькая' modifies the noun 'комната', describing its spatial characteristic.