A Book Cover in 5 Iterations

I've revamped most of my book covers once or twice over the years, but none have gone through more transformations than my time-traveling detective novel BackTracker. Here they are, from the very first to the latest, which just went live this week:

The first one was all about that noir; the second emphasized the hard-boiled detective; the next two focused on the time travel aspect; and the new one places the futuristic setting front and center. Tough to pick a favorite, but I'll stick with the current iteration for a while and see how it does.