Mercer is primarily a writer focused on the gothic scene and its music.
During the 1980s, he wrote regularly for the British music weekly Melody Maker, and edited Siren magazine in the 1990s.
He has written five books on gothic music, in addition to numerous self-published material.
Mercer's Music to Die For compendium (2009) was described by The Quietus as having "a far greater stylistic variety than the casual observer might imagine", and as being "stuffed full of the best and most artistic music the world has to offer".
[1] The second and third books spawned a series of CD compilations, with detailed sleeve notes provided by Mercer.