One Bullet One Heart is one of Castle's bestselling novels, written in the years before he met Beckett. It is one of his 'standalone' books, not part of the Derrick Storm series. Although is not directly referenced in the show, it is mentioned in his bibliography on richardcastle.net
(From richardcastle.net) Over the last decade, psychologist Norma Kent has treated the full gamut of mentally unstable patients. But no one has ever shaken her to the core like Jason Reese. A former juvenile offender who served time for shooting his girlfriend, Jason is pure alpha male – all untrammeled ego and hormonal drive, with nary a trace of remorse. So when eligible young ladies start showing up dead – with a single bullet through their hearts – Dr. Kent can’t help but suspect her most notorious patient, particularly when he starts complaining that all the dates he’s had lately have been bloody disasters – and he’s got the scratches and scars to prove it. As Norma starts to look into Josh, the killer starts to focus his attention on her. Is it merely coincidence or has Josh returned to his homicidal ways? Can Norma discover the true identity of the killer in time or will she find herself the next victim of this high-caliber heartbreaker?
References in Episodes
Mentioned on richardcastle.net