This book does a decent job of imagining what will go wrong if we give Russia what they want with a peace treaty. It takes place in 2033 and has the Ukraine war ending in 2025 with Russia keeping what it’s taken with no security guarantees for Ukraine.

It starts with a timeline of 2025-2033. Putin dies and is replaced by a more cunning nationalist who takes lessons from the Ukraine war.
Russia spends 8 years rebuilding their military after the Ukraine war ends in 2025. The lessons that the Russians take from their attempt in Ukraine is that they went in too violently, not giving the Ukrainians a chance to surrender Crimea style.
In 2033, after Europe and NATO have gotten complacent again and isolationism has taken hold in the United States, Russia plans to walk forces peacefully over the Estonian border and dare NATO forces to fire on them.
This results in awkward standoffs before anything happens and then, a small Estonian and American force must hold until NATO can actually react as a whole.
Over all, very plausible scenario and the military writing is well done. Quick read, definitely recommend.