The Thought Pushers, by Dima Zales, I noted that, due to the story losing a little steam after book one, I probably wouldn't be rushing into book three of the series. And I didn't. But I did take a look at what is colloquially called "book 0," a short story called The Time Stopper. I'd already downloaded it into my e-reader (for the unbeatable price of free), and it was short enough for me to read in about an hour.
The Time Stopper shifts focus to another character in the series, vengeance-driven Mira. In a story set before the events of the first book, Mira worms her way into the underworld of the Russian mob looking for clues on her hunt for her parents' killers. In a breezy few dozen pages, she gets herself into and out of trouble, leading toward the events that begin book one of the series.
Despite being set earlier in the chronology, this really isn't meant to be read first by anyone considering the Mind Dimensions series. Those books turn on the ignorance of main character Darren, whereas this story's heroine Mira knows all about the world of psychic abilities. Of course, the flip side of that coin is that here, because the audience knows she goes on to be a major character in the series, there's no real sense of danger to anything she does here in this prequel.
But then, to what degree this story has appeal, surprise isn't meant to be it. With the main series told entirely by Darren in the first person, the point here is to get inside the head of another character. It may in fact help improve subsequent books in the series. It's not like there was much mystery to what made Mira tick in the first few books. Still, writer Dima Zales was probably projecting a little too much of himself (or his own wish fulfillment) into Darren, which makes Mira's point of view here a nice change of pace. If it informs the characterization going forward, it's all for the better.
There's nothing truly essential here, but if you make it through the first two Mind Dimensions books and find them even modestly engaging, you've nothing to lose in this short side trip. I give it a B-.