The Occultation ( غيبة ghayba) in Shia Islam refers to a belief that the messianic figure, or Mahdi, who in Shi'i thought is an infallible male descendant of Prophet Muhammad, was born but disappeared, and will one day return and fill the world with justice and peace.
1. Imam Al-Mahdi ( AS) during his major occultation meets , teaches, and helps people , but people do not recognize him during the meeting but very few of the very pious believers who have a high degree in faith and know him.
2. Pious believers never claim nor disclose meeting Imam Al-Mahdi (AS). Pious believers know that Imam Al-Mahdi (AS) must be away from the enemies, so they do not disclose any information about him.
3. Those who claim in public that they met Imam Al-Mahdi (AS) or brought a message from him, can never be trusted.
4. Hundreds of very pious Ulama and believers have met Imam Al-Mahdi (AS) in hundreds of occasions. Many books were compiled in this subject by great scholars like Al-Muhaddith al-Noori in his book Dar Assalam and others.
5. We pray in Du'a al-'Ahd دعاء العهد to be granted seeing the face of our Imam Al-Mahdi (AS): اللهم أرني الطلعة الرشيدة والغُرّة الحميدة واكحل ناظري بنظرة مني إليه.
This means that seeing him during the major occultation is possible for certain very pious persons.
Thanks for your question.
There are many interesting and well-written books about Imam Mahdi (aj).
I recommend the following ones:
Al-Imam al-Mahdi, The Just Leader of Humanity
An Inquiry Concerning Al-Mahdi
The Promised Savior: An inquiry into the imamate of Imam Mahdi (as) from the viewpoint of Muslim thinkers
The Occultation of the Twelfth Imam (A Historical Background)
That is just one small portion of texts concerning Imam Mahdi (aj) that can be found at Al-Islam.org, there is a whole section dedicated to him (aj):
Hope this is helpful inshaAllah.
Every community needs a perfect leadership to guide them to the right and avoid them from the wrong.
Allah The Glorious Has ordered people to follow the prophets then their successors. The last successor of the Prophet Muhammad (SAWA) is Imam Al-Mahdi (AS) who is at present under occultation by order of Allah (SWT) because of certain circumstances. Imam Al-Mahdi (AS) himself ordered the followers of Ahlul Bayt (AS) to follow during his occultation the most learned pious Ulama. (Wasaa'il al-Shia, Volume 27, Page 131.
Some persons misunderstand the meaning of Taqleed and ask about its validity . We invite them to think :
1. Is it possible for any Muslim to claim that Allah, The Most Glorious wants to leave the Ummah with out guide during the occultation of the Infallible Imam ?
2. Who is the best to guide the Ummah better than the most learned about the teachings of Ahlul Bayt (AS) with piousness?
3. Who can guide the Ummah to Islamic rules on new issues during the occultation better that the most learned and pious, who are the Maraaje' of Taqleed?
No community can remain protected from deviation if they do not follow a pious leadership and there is no leadership in the whole world more pious than our Maraaje' of Taqleed who have the maximum knowledge about Islam and highest level of piousness.
No. This claim is untrue.
All our scholars accepted every message from Imam Al-Mahdi ( AS) which came through authentic source like the four emissaries.