never had much contact with shias, trying to understand

does anyone (especially reverts) have good resources for people who don’t know much about islam to understand twelver shi’ism? i am trying to understand the concept of the hidden imam but much of what i’ve seen online so far doesn’t make much sense to me due to my lack of exposure. is there something like “islam for dummies” that discusses this? i am from the american south so not many muslims to ask around here. thank you.