Best Defense
(Star Trek: Legacies #2)
by David Mack (2016)

Una ventures into a parallel universe to save her old shipmates, exiled there decades earlier by a mysterious device called the Transfer Key.

Meanwhile along-awaited Klingon-Federation peace conference convenes, with Ambassador Sarek and Councillor Gorkon.

But both sides have enemies who would prefer the two great powers remain at war. Then along comes Kirk…

David Mack has done some great Star Trek novels, including S.C.E. novellas and the series Destiny. This one is great too. Everything slowly ramps up to an action filled third act where the Enterprise takes on the Romulans and the Klingons.

But someone has to be taken into the parallel universe to justify the third and final book in the series….