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The Doctrine of Arius
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Arius: Heresy and TraditionArius: Heresy and Tradition by Rowan Williams
Buy new: $29.92 / Used from: $14.00
A good book on Arius divided into two parts: History and Doctrine. Focused on his person and his writings. Somewhat wordy and a slow read, but worth the investment.
Early Arianism--a view of salvationEarly Arianism--a view of salvation by Robert C Gregg
Buy used from: $11.68
I found this book at Half-Priced Books. It is a good one. Very Scholarly, but easy to follow. I highly recommend it.
Restoring the Biblical Christ: Is Jesus God?  Volume OneRestoring the Biblical Christ: Is Jesus God? Volume One by Jason Kerrigan
Buy new: $14.99 / Used from: $17.52
This book is written from an Arian perspective. It presents Scriptural arguments that support the Arian position and exposes/refutes arguments (mainly Trinitarian) that oppose. Beginning with John 1:1, the book refutes a great number of Trinitarian Scriptural misconceptions. Well worth the read.
When Jesus Became God: The Struggle to Define Christianity during the Last Days of RomeWhen Jesus Became God: The Struggle to Define Christianity during the Last Days of Rome by Richard E. Rubenstein
Buy new: $10.20 / Used from: $2.97
A good historical overview of the events surrounding the Nicene Council/Creed. Easy to read (reads like a novel). Very informative and largely unbiased. Highly recommended.
The Search for the Christian Doctrine of God: The Arian Controversy, 318-381The Search for the Christian Doctrine of God: The Arian Controversy, 318-381 by R. Hanson
Buy new: $37.12 / Used from: $29.98