What all are the important books, that are part of Buddhism, other than Dhammapada?
This depends on which Buddhist school or tradition you are referring to.
For the Theravada school, the main scripture is the Pali Canon or the Tipitaka, in the Pali language. Tipitaka means the three baskets. The three are the Sutta Pitaka which is the basket on the teachings of the Buddha and his disciples, the Vinaya Pitaka which is the basket on the monastic rules, and the Abhidhamma Pitaka which is the basket of philosophical analysis.
Here's one view of it below. The Dhammapada is only one book of the 15 books of the Khuddaka Nikaya, which is part of the Sutta Pitaka.
There are also the commentaries to the Tipitaka and other supplementary writings, such as the Visuddhimagga.