This is my favorite one so far! I think Greenwood hit her stride here (hopefully not her peak) by giving Phryne a lengthy, complex and dangerous trip that was somewhat tangential to the main story.
I like that Greenwood always has more than one story going on in a novel, and in this case I was never distracted from the main story because the adjacent story involved this crazy trip. I know nothing about flying small prop planes (and certainly not those from the 1920s) so I appreciated the amount of detail Greenwood provided (and the research she did) to make this come to life. I also now wish I had visited the Australian Alps while we were there a few years back. It sounds stunning - remote, impressive and refreshing.
I will keep going. Only 15 more to go!