On camera, the actor Richard E. Grant tends to emit an unknowable, tenebrous quality: No matter how much his characters express, you always sense something between the lines that can’t quite be calibrated. In his new memoir, A Pocketful of Happiness, Grant elegantly summarizes his career as several decades of “minimalist villainy.” His characters have run the gamut from hedonistic wastrel thespian (Withnail and I) to authoritarian girl-band manager (Spice World) to utterly charming criminal accomplice (his Oscar-nominated turn in Can You Ever Forgive Me?), but if they share an attribute, it’s that you wouldn’t be even a tiny bit surprised if they stole your wallet. In life, though, Grant has turned honesty into an inventive, impossibly delicate art form. Almost two years ago, his wife of 35 years, the dialect coach Joan Washington, died from lung cancer, and in the immediate months after losing her, he turned to Instagram to record fragments of his bereavement. In a typical video, his face is slightly off-center, his gaze away from the camera. He looks disheveled. He …