I don't remember The Green Ghost specifically which might be a bad sign because I do remember some of them quite clearly. I'm trying to remember without going down to the basement, but I thought that all of the ones under the Robert Arthur name were early ones in the series. My memory is that the series was better at the point when the books still opened and closed with the boys meeting with Alfred Hitchcock.

I think the one that stuck with me the most was the one with 'Silver Spider' in the title. It wasn't really a mystery so much as a Ruritanian adventure which really didn't fit at all with the rest of the series but was something that small me thought was just amazing and ever so much more interesting than stuttering parrots or screaming clocks.

I remember buying some of the newer books in the series at one point for my younger brother (eleven years younger than I) and then reading one and finding it really terrible. I was relieved that, when I went back to the earlier books in the series, they still had clever puzzles and at least a smidgen of character depth.