Mara Jade was one of the most polarizing figures in the Galaxy. Some people saw her an interesting person and a strong role-model, and they wanted to have sex with her. Others saw her as an annoying bitch who ruined Luke Skywalker and the Jedi Order, and they wanted to have sex with her.
The Emperor had lots of hands. They did things he was unable, or unwilling, to do with his own hands. Mara Jade was one of his most useful hands. The Emperor took her when she was very young and trained her to use the force and perform other duties as assigned. Her most useful skill was that she could hear Palpatine through a telepathic link anywhere in the Galaxy. This was slightly easier than the many other forms of Interplanetary communication that were readily available. Mostly Mara was sent on assassination jobs, but occasionally she got to do other stuff like spy on Darth Vader, or seduce old men. She once killed a man, however, when he joked about the Emperor giving her a "Hand job." Eventually she was ordered to fo the Jabba's Palace and kill Luke Skywalker. She failed, and allowed Luke to go on his famous rampage. She dreaded turning in her mission report to Palpatine, but, fortunately, he was killed a few weeks later.
Around this time, Grand Admiral Thrawn took over what was left of the Empire. Seeing an opportunity to return to an employer who encouraged revenge killings, Jade met with Thrawn and offered her services. She was disgusted to find that Thrawn double-crossed her to capture Karrde. Disgusted! Since she only knew two people in the enitre Galaxy, she turned to Luke for help. Even though she openly promised to kill him, Luke helped her because it was the first time a girl that wasn't his sister had talked to him. He really hoped Mara didn't turn out to be his sister. After a complicated plot involving clones, Mara and Luke saved everybody and Mara no longer felt the need to kill him.
By now she had become a Jedi, and took Jaina Solo as her apprentice. At the beginning of the Yuuzhan Vong nonsense, Mara contracted some crazy disease. Lando was a bit nervous but convinced everyone that he was clean. While she was recovering, Mara hung out with Anakin Solo a bunch since he was superfluous anyway. After her illness cleared up she discovered that she was pregnant. Again, Lando went out of his way to convince everyone that he had nothing to do with it. Mara did stuff, then gave birth to Ben Skywaller, then did some more stuff, then theYuuzhan Vong were defeated.