I'm not familiar with many good surveys of pre-Viking Age Scandinavia, but Lotte Hedeager's Iron Age Societies. From Tribe to State in Northern Europe (1992) might do the trick. There's also Judith Jesch's (ed) The Scandinavians from the Vendel Period to the Tenth Century (2012) (table of contents), which I haven't read. It won't have the same continuous flow of narrative that Hedeager gives and will likely read a bit drier, but it is a bit more up-to-date with current archaeological evidence and seems to be a fairly evenhanded survey. If you're willing to cast your net a bit wider, I really enjoyed Patrick Geary's Before France and Germany (1988), which is deeply rooted in the scholarly debates of the '80s and '90s but which helped stoke my interest in pursuing higher degrees in history. Chris Wickham's Inheritance of Rome (2009) or Guy Halsall's Barbarian Migrations and the Roman West (2005) are more updated visions of this period of time.

If you're looking into pre-Viking Scandinavia, you'll have to wrap your head around how Scandinavian scholars refer to different periods. Wikipedia actually charts it out pretty well. The Iron Age (300 BC-800 AD) refers to a long period before the Viking Age (800-1050). You might see Roman Iron Age (1 AD-500) or Later/Younger Iron Age (500-800). This same period is also divided into the Migration Period (300-600; based on reports of people moving into the disintegrating Roman Empire), the Merovingian Period (450-750; named after the ruling family in the old Roman province of Gaul/France), and the Vendel Period (550-800; named after the village of Vendel in central Sweden, where archaeologists excavated a rich cemetery that has become an icon of pre-Viking Scandinavian culture). Whatever book you pick up, take careful note of the years the authors are discussing, since vague references to these periods sometimes obscures rather dramatic change.

Also, Tactius' Germania is a must read for any enthusiast or scholar of early northern Europe—but it can't be taken at face value. Tacitus certainly does preserve some authentic information about Germanic tribes, but he manipulated this information to produce an implicit critique of contemporary Roman society. It's also worth remembering that Germania was a Roman concept and probably meant very little to the 'Germans', similar to how someone from modern-day America might think that both Algeria and Afghanistan a parts of the "Middle East." I'd highly recommend Christopher Krebs' A Most Dangerous Book (2011), which traces how Germania was written and how it's been used in modern scholarship and political propaganda. It's an excellent read!

/u/alriclofgar – recommendations on early Anglo-Saxon England?