June 6. On this date in 2013, the Universal House of Justice sent an email to an individual believer concerning the number of texts written by the Báb, Bahá’u’lláh, 'Abdu’l-Bahá, and Shoghi Effendi, noting "A fraction of the total numbers of unique works have been published in the original languages or translated into Western languages."

June 6. On this date in 2013, the Universal House of Justice sent an email to an individual believer concerning the number of texts written by the Báb, Bahá’u’lláh, 'Abdu’l-Bahá, and Shoghi Effendi, noting "A fraction of the total numbers of unique works have been published in the original languages or translated into Western languages."

The Kitáb-i-Aqdas, the central book of the Bahá'í Faith written by Bahá'u'lláh, was only officially translated into English in 1992, by which time other translations, such as one by the Royal Asiatic Society, were becoming increasingly available through dissemination via the internet. My personal opinion is that the material in the Kitáb-i-Aqdas is so objectionable that the Bahá'í authorities wished to shield Western believers from its contents, as they do from Bahá'u'lláh's other works by not providing translations.

The Universal House of Justice Department of the Secretariat Transmitted by email 6 June 2013
Dear Bahá’í Friend,
Your email letter dated 3 April 2013 requesting statistics concerning the Sacred Texts has been received at the Bahá’í World Centre and forwarded to the Research Department for study. That Department notes that the collection and collation of the Sacred Writings is an ongoing process, and the numbers are continually being revised. The estimates of the numbers of unique works can be given as follows:
For Bahá’u’lláh, nearly 20,000 unique works have been identified. Most of these Writings have been collected; however, 865 are known to have been revealed, but the texts are not available. Close to 15,000 of the collected works have been authenticated by the Archives Office to date.
For the Báb, over 2,000 unique works have been identified. Most of these Writings have been collected; however, 74 are known to have been revealed, but the texts are not available. Nearly 1,600 of the collected works have been authenticated.
For ‘Abdu’l-Bahá, over 30,000 unique works have been identified. All of these Writings have been collected and over 27,000 of them have been authenticated.
For Shoghi Effendi, over 22,000 unique works have been identified. All of these documents have been collected and the majority of them have been authenticated.
It is estimated that approximately ten per cent of the documents described above are in photocopied form. A fraction of the total numbers of unique works have been published in the original languages or translated into Western languages. However, citing exact numbers would be misleading since much of the unpublished and untranslated material consists of day-to-day correspondence and personal guidance and encouragement, which is less likely to be of general interest. The World Centre is actively pursuing a publication programme for the as yet unpublished major works of the Central Figures of the Faith and Shoghi Effendi.
With loving Bahá’í greetings, Department of the Secretariat

To summarize rules of Bahá'í translations...

Arabic works cannot be translated into Persian.

Persian works cannot be translated into Arabic.

Persian and Arabic works can be translated "into Oriental languages such as Turkish and Urdu."

Persian and Arabic works can be translated into English.

Persian and Arabic works cannot be translated into European languages.

English works can be translated into European languages.

For further reading, please see "Persian, Arabic, and Provisional Translations", "Translation and provisional translations", "Unveiling the Hidden Words, by Diana Malouf: Commentary on "Translating the Hidden Words,' review by Franklin Lewis", a letter dated June 27, 1933 from Shoghi Effendi to Adelbert Mühlschlegel about Bahá'í orthography, a letter dated June 30, 1999 from the Universal House of Justice outlining its procedures for approving provisional as opposed to authorized translations, a letter dated May 13, 1986 from the Universal House of Justice to the Spiritual Assembly of Guadeloupe, and a letter dated February 15, 1957 from Shoghi Effendi to French Bahá'ís.