I will fully admit to picking this up in the first place because of the constant references in Spider Robinson's books to the Travis McGee novels. You gotta be in the right frame of mind, but this was the most delightfully pulpy hardboiled mystery I think I've ever read. Yes, it suffers a little bit from a particular brand of 1960s machismo that renders all women as vaguely alien figures, but these are pretty well-sketched, distinct alien figures, I gotta say. The women revolve entirely around the men in the plot, but other than Travis himself and the bad guy, almost every character with a speakin role is female, and they even go a bit beyond The Vamp, The Victim, or the Vixen.
Plus some of McDonald's turns of phrase are absolutely face-slappingly perfect. This is the style that so many have imitated but rarely duplicated.