Grisly, indeed - but actually kinda compelling. At least to modern readers; for a long time this story was - and I believe is sometimes still - left out of Sherlockian collections because of its content.
Even Doyle was reportedly distressed at what he'd written and agreed that it should be suppressed.

Which led to the the fact that this story was suppressed and reportedly did not have an original American publication - a fact which has led to the numerous bastardized editions of the canon (actually and unfortunately comprising the vast majority of current commercially availible editions of the Sherlock Holmes stories) in which "Cardboard Box" and "Resident Patient" have the exact same beginnings.