Star Trek: Enterprise: The Romulan War, book 2 : To Brave the Storm
Michael A. Martin2011

The Coalition of Planets has shattered, with Vulcan, Andor, and Tellar abrogating the treaty. Their pledge to come to the mutual defense of any power that is attacked has been shunted aside. Horrified by how easily the Romulans can seize control of their advanced starships, turning them into weapons, Andor and Tellar have joined Vulcan on the sidelines. Humanity is now the only thing that stands between the Romulan Star Empire and total domination of the galaxy.

To drive humans from the stars, the Romulans employ ruthless and murderous tactics... and even dare to strike on the Vulcan homeworld with the hopes of demoralizing their Vulcan brethren. Heartened by their victories, the Romulans carry their all-out war assault closer to the heart of humanity–Earth.

But the tattered remains of Starfleet stand unwavering, with the resolution that never again would any enemy strike ever reach Earth. On the front lines of the Earth-Romulan War is the United Earth flagship, the Starship Enterprise. Her captain, Jonathan Archer, has seen his vessel of exploration become a battleship. Once hailed for his work bringing the Coalition of Planets into existence, Archer is now a pariah. Undaunted, the captain keeps fighting, searching for allies and determined to do his duty: to save Earth and forge a new federation of planets.