Dave Mustaine has announced the release of his new memoir, "In My Darkest Hour", which will be published on September 8, 2026, via Grand Central Publishing's Da Capo imprint. The book, co-written with journalist Joe Layden, details Mustaine's 2019 diagnosis with squamous cell carcinoma at the back of his tongue and his journey through cancer treatment, including 51 radiation sessions and nine chemotherapy treatments. Mustaine overcame the illness and returned to performing in early 2020, before the pandemic disrupted touring.

The memoir chronicles how Mustaine continued making music during treatment, completing the recording of MEGADETH's sixteenth album, "The Sick, The Dying…And The Dead!", which was released in 2022. Mustaine described the experience as a mental and physical battle, noting the effects of "chemo brain" on his memory and the fear of losing his ability to breathe or function. He emphasized that the book is about the person behind the music, not just the career.

Mustaine revealed that the book was inspired by his desire to share hope with others facing serious illness, especially given his personal experience with Alzheimer's in his mother-in-law. The memoir will be available to the public on September 8, 2026, and is described as a deeply vulnerable reflection on confronting death and maintaining creativity.

Da Capo, a music-focused imprint, is the reincarnation of Da Capo Press, which was acquired by Hachette Book Group in 2016. The imprint was dissolved in 2024 as part of Hachette's restructuring, but has since re-emerged to publish this memoir. Mustaine previously authored "Mustaine: A Heavy Metal Memoir" (2010) and "Rust In Peace: The Inside Story Of The Megadeth Masterpiece" (2020).