Juxtaposition: putting things together to make something "more than the sum of the parts" is a common artistic skill, it is common (but often unrecognised) in the Bible. As my least favourite book of the Bible helps reveal!
It is certainly one of my favourite Bible passages, indeed it is many people's favourite Bible chapter. Isaiah 40 is just full of superb phrases and pictures. Whenever it was composed, this chapter really comes to life and sparkles when it is heard as the Judean exiles in Babylon heard, it just before Cyrus the Persian king captured the city. For a better idea of the background watch the Video "Babylon as background to hearing Isaiah 40" (4MB).