There are some records in the history of rock that one might characterize as essential. This is one of them. We are now talking about rock as a form of music which try to catch the pulse of society and hopefully invent new ways of expressing it. This record represent creativity and boldness. Bowie was by the mid seventies not a very healthy person beeing a drug addict. He came home to Europe from the US and started a very fruitful cooperation with Brian Eno and some other great musicians. The record is divided in two main parts. The first half contains in a way ordinary rock songs but they all have the extra something that makes them extraordinary. One can hear they are made of nerve and blood from a man that is struggling with himself. The other half of the record is instrumentals and the influence of Brian Eno's treatments is more evident here. Heavy moods and atmospheres makes them different from ordinary rocksongs, but still you can hear that they have spine and structure as usual Bowie-material.
What makes this record special is the influence it had on modern rock music with it's inegrity and honesty, and it is clearly a proof of the fact that rock can have a position alongside other ways of expressing art (like paintings and theatrical performance).
If you like contemporary rock that turned out to be milestones in it's time, this is a record to check out. Many records of today are influenced by this music made by Bowie, like U2 and their record Zooropa. Bono is a great admirer of Bowie's and Enos work during the 70ties, and this record is maybe the one that is most important of them.