Yeah, I kind of assumed that everyone didn't really care for the second one, and found the forth unsatisfying, but then I ran into a bunch of people who love 2&4 more than any of the others, and only started to get fic-writing levels of fannish about it after #4. There's also a pretty hot debate about how overtly slashy Peter and Thomas are. I don't read them as that slashy, but apparently they ping some readers pretty hard, who then rec the series on that basis.

tbh, I tend to acquire the new books on UK release, and then buy them when they come out here