I study everything. I mean everything. It's why I am so awesome.
From the dawn of Mesopotamian civilization to the Arab Caliphates, to the Yuan Dynasty in China, to the Kushites in Egypt, the Visigoths in Spain, the Mexica/Aztecs in Mexico, the Lombards in Italy, the Magyars in Hungary, and the Bretons in...well...Brittany (they're closet celts).
All these periods and people coalesce into each other, but of course it is awesome to study them in isolation as well.
Favorite period is the "transitional" period known as the Dark Ages. Essentially, the lack of centralized government, the fall of Roman Engineering and infrastructure and the rise of a new sort of cultural values that would eventually blend with those of the Romans.
On the flipside, studying the surviving Roman Empire in this period is truly rewarding (remember, Rome never fell, it just switched continents).
any ideas? i think reading about the Mongols or Timurids or something would be cool. I wanted to read about augustur caesar or hannibal but all the biographies on them seem crappy.
Julius Caesar is a good guy to study.
This
book is an excellent place to start. Adrian Goldsworthy is one of the premier classicists and military historians.
The Byzantines/East Romans are always good as well, if you want a general/relevant history,
this book does a great job tying it all together. The author draws parallels between the East Romans and the U.S. which everyone likes doing, but he does it in a fairly balanced way.
Essentially, his book is very constructive and enlightening.
Hadrian has a good biography, not read it yet, but it's been highly praised.
link
Same author has a bio on Augustus
here
I recommend Goldsworthy because I have read him and he is awesome. He does a great job telling a good tale, but doing so accurately and making scholarly concessions along the way.