There are hundreds books to read; but I would recommend starting off by reading about the life of the Prophet (s) (from Shi'i authors, as Sunni biographies are based upon narratives that are rejected by Shi'i scholars). It is also recommended to get some hadith collections. There are many articles on sites such as Academia.edu that talk about late antique society - what society was like at the time of the emergence of Islam. A book of fiqh will also be important, so that the person gets some ideas of the laws; and books on spirituality. They should also get two or three Qurans that include a tafsir, otherwise it will be hard for them to understand it. There are many introductions to Shi'i Islam by various authors.