The reason is that, in addition to what is probably the best song from the FB&TC self titled album, this single features 3 songs which are among the best Frank wrote at the time.
ALL MY Ghost (alas, without the cute 'Green Hill Hymn' from the album version), is first, a mid tempo song with cool chord shifts (listen to the noisy intro), and cooler lyrics, where Frank meditates about living forever. In typical Frank fashion, the results are surprising, including meditating on the bible and finding revelation in a porno store!
The second song, Living on Soul, is punkier, and used to be a live favourite for a while. It is a song about losing control, with cool guitar licks. Humbult County Massacre is one of Frank's historic songs (like St. Francis Dam Disaster and Heloise). Live, it becomes a template for Frank's screams, but this version is every bit as powerful, even if it is most restrained.
However, the absolute highlight of the collelction is the amazing cover of Bob Dylan's The Changing of the Guards. The song (from Street Legal), is one of Bob's lesser known masterpieces (although it does feature on two 'greatest hits' compilations). It really is a masterpiece of a song, with one of the mose amazing riffs (played with a Sax on the original and with the guitar here), and powerful lyrics ("Gentlemen" he said "I don't believe your organization, I've shined your shoes, I've moved your mountains and marked your cards, but eden is buring. Either brace yourself for elimination, or else your heart must have the courage for the changing of the guards"). Frank Black and the Cs version, stripping away the layers from Dylan's Vegas-y treatment, allow the sheer power of the song to shine through. In my opinion, this is one of the best Dylan covers out there.
'All My Ghosts' is not the place for Frank Black beginners. However, if you already like him, it is a fantastic buy, even if you are not a fanatic.