Level 7 (1959) is a little gem I'm glad I stumbled upon.
The novel is in the form of a diary by Officer X-127, a nuclear launch officer who is responsible for initiating a global thermonuclear war, and traces his mental transformation from being proud to have been selected for this important assignment to coping with his responsibility for the end of the world. It is a realistic, grim, and dark view of the politics and consequences of nuclear war that is a worthy contemporary to On the Beach.
One cautionary note about the novel. Level 7 is not set in a traditional nuclear launch missile silo, but in a dystopian-style, self-contained underground fallout shelter that also serves as the missile launch center. While at first it seems to detract from the authenticity of the novel, and the descriptions of this complex may be extensive, the location is an integral part of the plot.
The Library of American Fiction's edition of Level 7 is a comprehensive work that includes insightful commentaries about the book; the original prologue to the novel that was not included in the printed edition (personally, I think the original prologue detracts from the overall work); as well as extensive notes and a Further Reading section.