Yeah, they fought 3 times in the novel, the first Dooku won, the second and third Vos won.
The first fight more or less went down like this: Vos and Ventress attack Dooku, they're pretty even until Dooku recognizes that Vos's fighting style is the same as Ventress's, whom he trained, so he capitalizes on it and gets the upper hand. Ventress is hurled against a wall with the force and passes out, so Vos gets pissed off and manages to disarm Dooku. But he hesitates a but too much, thus giving Dooku the opening to make a come back and disarm Vos too.
The second time was brief and intense: it took place several months after the first duel, and after Vos had been trained by Dooku for a while and became his dark disciple. While in the first duel Vos had been hindered by emplying a fighting style which Dooku was familiar with, this time Vos is able to overwhelm Tyranus thanks to his unpredicatble fighting style and disarms him.
The third time Vos quickly defeats him again but DOoku had one arm broken so...