According to Wiki, there are several books between them, but they are all in order. It just seems as though there was more backstory in Nemesis than in Mercadian Masques. Like seriously in Mercadian Masques it refers several times to some of the people who had been left behind on Rath, when the Skyship Weatherlight jumped planes, and the character who held the portal open, the mage guy who's name escapes me now, fell into the rigging of the Predator, and Mirri, cat warrior, and someone else were left in Rath. This was all explained in Nemesis, however it was mentioned in Mercadian masques as leaving the characters behind.
Now how can you leave characters behind in the first book, then explain how they are left, and build story lines around them in the next book?
Also, what happened to Mirri, Cat Warrior?