I just watch the TV Zeigen when I can, but I've read the Bücher and I know that they're super different. Relatively what book are they at in the TV show? Have they figured out who the first A is?

The A's are different in the Zeigen and Du do not know who A is Von the end of season 1. As for what book they are up to Von the end of the 10th episode they have finished book three and from there they are moving in their own direction. Some things are the same such as Ian's body disappearing but they have also introduced characters that are not in the books.
Hope this helps