The series of introductory books is still available as ebooks from $0.99 and as paperbacks from $5.70. Most ebooks have been updated this month. Just redo the download to get the latest version.
Note: some will be available without charge for a day or two around month-end.
The booklets in the series are:
The Bahá'í Faith - A Short Introduction
The Bahá'í Faith - A Short Introduction for Christians
The Bahá'í Faith - A Short Introduction for Muslims
The Bahá'í Faith - A Short Introduction for Hindus
The Bahá'í Faith - A Short Introduction for the Seeker
The Bahá'í Faith - A Short Introduction for Women
And the related books:
The Bahá'í Faith and the Cosmos – A Short Introduction
The Bahá'í Faith and Life After Death
Bahá'í Books - A Short Introduction