Book 3 of 4 in the first Star Trek: Section 31 mini-series.
"Once, in order to preserve the galaxy's fragile balance of power, Captain James T. Kirk carried out a dangerous mission to capture a cloaking device from the Romulan Star Empire. Months later, while investigating a mysterious disaster aboard a Federation starship, Kirk discovers that the same technology he obtained for the sake of peace is being put to sinister purposes. What the crew of the Starship Enterprise™ uncovers will send shock waves through the quadrant, as Section 31 sets in motion a plan that could bring the major powers of the galaxy to their knees."