The Kirov series is over fifty books long and counting. But the third entry, Pacific Storm, was planned as a potential stopping point, according to the introduction of a later entry. And while I normally criticize series from Jack Ryan to the Survivalist for passing good opportunities to conclude, it’s for the best that this one sailed right by it.
After having fought through the Mediterranean in the second book, the missile cruiser battles in the Pacific in the third. Besides the issues with the prose, the encounters fall short because the disparity between World War II ships that don’t know what they’re dealing with and a futuristic warship that does means that all the battles have to be contrived in some fashion. Pretty much the only things that work are various surprise gimmicks, close range, and pure numbers, and that’s barely enough to sustain a three-book series.
The ending still involves sequel hooks, but features the ship going back to its present with its crew having realized they started the (nuclear) World War III by firing on an American submarine. When they see the submarine after their “excursion”, they avoid attacking it. Meanwhile, their experiences have changed the “past” significantly. This would be a perfectly good conclusion that still gave room to continue, but it would have concluded three stilted, modestly out-there books. Instead, the series got bigger, more complicated, and, yes, better.