[ceceron]

IMHO this kind of list defeats its purpose. Being popular / having high rating in the popular services is definitely not an accurate marker of being "mind-expanding". In fact, I would expect most of them be rather safe/easy/conforming to what people find acceptable, therefore not challenging their minds. Just looking at the philosophy section of the list proves the point. Also the sci-fi part is surprisingly poor in substance — one would think that technical people should be well-versed in that particular genre.

I would prefer to read a list curated by a single "expert" person. Such a list would be shorter, more biased, but hopefully not so bland. For example, Eli Bendersky puts every now and then a nice summary of his impressive reading adventures.