It really depends on the person who is reading it in the end.
The most important thing (and the problematic) with those stand alone series, is that it needs to be at the same level/quality of the main story or better.
Since if people decide to read it, they will actually expect the same standards.
At least, this is what I think. One of my favourites shows got a second season, but it was more of a stand alone show with a whole new casting and plot. And expect from the location of the story it didn't have any connections to the original season 1, and sadly the plot didn't live to the expectations and I and most of the people who I know that watched the show stopped.
And it is also the problem with sequence movies, that sometimes they can't live to the standards that the first movie set.
So basically, you can't know if you are going to fail or success in this. Just gotta be careful 
And what I meant by similar. Is that you said it had the same vibe/genre as your main story.