Invincible is a rather unique story, spanning 2 e-novellas, because it's told entirely in the form of log entries and/or letters which takes some getting used to.
Basically it's about Gomez's solo-mission to a crystal planet in Nalori space to help establish a way to mine that planet's mineral ressources. She's faced with prejudices due to her being a Starfleet officer and a woman, and with legends about the place being cursed by giant monsters which turn out to be semi-true. It's an interesting experiment of story-telling. As a reader you get everything second hand, the description of the planet, the flora and fauna, and the events are told in retrospect - and it works for the most part.
I'm just not sure I really like Gomez, to be honest. Granted, she's competent, but she displays quite a superior attitude in this story, criticizing the Nalori for their backwater attitude and technological capabilities as well as the living conditions on the planet (What's so bad about living in a tent?). That's not to say that she's not factually right, but, as was the case with the other members of the SCE in Cold Fusion towards Nog, there's a certain arrogance that comes from being part of the cool genius-corps of engineers, that rankles. Not everyone is an idiot just because they don't belong to the SCE or Starfleet in general! Nog at least had the advantage to have the required knowledge about Empok Nor and therefore stand up to the SCE-members - which wasn't the case here. And I have to wait and see how that is going to play out in future stories because that could develop into a major turn-off for me.
Apart from that attitude-problem, this is a sort of a "coming of age"-story for Sonya Gomez that throws her into the deep end without a safety net (in the form of ready backup) and rearranges her priorities regarding her personal life. And even though the story's told mainly in Gomez's logentries, the supporting characters are surprisingly 3-dimensional (apart from their status as idiots, mind you). Interestingly, the Nalori return in the Vanguard-series in the form of Ganz's executioner Zett.
Overall, good story - with the mentionned superiority-complex issue.