The Beast Must Die by Nicholas Blake

"Can you imagine yourself, hypocrite lecteur, in the position of being able to do a murder with impunity?"

After his young son is killed in a hit and run, his grieving father sets out to find the perpetrator and exact vengeance. Hiding behind his mystery writer persona, Felix Lane; Frank Cairns tracks down the man who drove off without confessing and his fair lady passenger. Seducing sexy actress, Lena, "Felix" finds his way to the murderer's house as a house guest, then things turn strange.

The first half of the novel is written in a particularly endearing first person diary format that draws you in. Amusingly enough the author cited on the cover is also a pseudonym, that of Cecil Day-Lewis, for more info click on the link.

When Frank sets out to commit his perfect murder, it appears it isn't quite so perfect. He hasn't killed anyone and now his diary threatens to send him away. Enter detective Nigel Strangeways to discover what's what and who is to blame.
 
This was a thoroughly enjoyable easy read that brings entertaining suspense and old school detective stylings.

5 out of 5 murders are never perfect.