can now be found at: http://art.fnal.gov/art-workbook/
If you are new to HEP data analysis...
Read Parts I and II (the introductory material and the Workbook) from start to finish.
If you are an HEP data analysis expert...
Skim Chapter 3: this is where key terms and concepts used throughout the art
document suite get defined. Skip the rest of the introductory material
and jump straight into running Exercise 1 of the Workbook.
If you are somewhere in between beginner and expert...
Skim the introductory material in Part I to glean what you need, but definitely read Chapter 3 "Introduction to the art Event Processing Framework."