You can start by exploring this link, and the sub-sections from it, that will lead you to many relevant books and articles.

https://www.al-islam.org/explore/shia-and-sunni

If you are looking for short Fact Sheets on various topics related to Shi'a belief and practice, then check this out:

https://www.al-islam.org/nutshell/

If you would like to sample the words of the Imams of the Ahl al-Bayt (a) when they speak of God, or address Him in supplications, then these two resources may be of interest:

https://www.al-islam.org/shiite-anthology-sayyid-muhammad-husayn-tabatabai

and

https://www.al-islam.org/sahifa-al-kamilah-al-sajjadiyya-imam-ali-zayn-al-abidin

Hope this helps!