David Wishart 
Germanicus 

Marcus Corvinus feels his heart sink when he is summoned by Empress Livia. Age has not sweetened her and she’s about as trustworthy as a snake with a migraine. But Livia has a way of asking a favour that is impossible to refuse — which is how Marcus finds himself investigating the death of her grandson, Germanicus. And uncovering a multi-stranded web of betrayal and deceit that threatens the imperial succession and even Emperor Tiberius himself.