Fall of rome is a frequent question here http://www.reddit.com/r/AskHistorians/search?q=fall+roman+book&restrict_sr=on&sort=relevance&t=all

There's this list from the book rec http://www.reddit.com/r/AskHistorians/wiki/books/europe#wiki_ancient_rome

The Fall of Rome and End of Civilization by Bryan Ward-Perkins (2006). A work that has quickly become a standard, it uses archaeology to provocatively draw a harsh line between the Roman and post-Roman world. It also functions as an excellent introduction to archaeology and the Roman economy.

How Rome Fell by Adrian Goldsworthy (2006). Goldsworthy is the author of numerous works of popular history and is very familiar with the form. He provides and excellent and detailed narrative, as well as an analysis focused on political systems.