Per the Publishers Weekly blurb on its webpage, Mike Hammer: Murder Never Knocks is the ninth Mike Hammer book produced by Max Allan Collins’ “posthumous collaboration with Spillane”. And Collins is, of course, a pretty well known author in his own right, and again per the webpage, is also Spillane’s literary executor. So you can make what you wish of all of that.
In any case, Murder Never Knocks is on sale for $0.99 in the US right now…