Bahá’u’lláh And the New Era by J. E. Esslemont is the standard introduction to the Bahá’í Faith in the United States. It is one of the first books I read about the Faith. It has been updated several times since it’s first publication in the 1920s.
Bahá’í Basics by Frances Worthington is a newer introduction to the Faith.
The Bahá’í Faith: A Guide for the Perplexed by Robert H. Stockman is also a 21st century introduction to the Faith that is slightly scholarly.
Websites – General Information
Websites – Bahá’í Writings
Websites – Bahá’í Writings, Scholarly Papers, and Commentaries