mark, acts, hebrews, 1 john, revelation, ezekiel? (i think),
because Yhvh has said what is happening today, before today happened, and what great love He has for His people, specifically is written, and is very true, very simply true , today, as it is written, and has not ever changed;
but men/mankind has messed it all up,
Yeshua was sent to be born a man, to die, and to be raised from the grave, so we could live today, on earth, like the believers/ekklesia did in acts et al, so also today , though rarely seen.
for very dramatic differences then and now for most, look up "union with" (ekklesia living on earth in union with God; not as if 'waiting' for Him some day by and by..... (though ekklesia wait daily for Yeshua's return ! looking for His deliverance that is promised, as well as what is already accomplished).
Okay, so if you could by choice, which book(s) of the bible (time era) would you want to live in and why?
....I'd say all, especially the four gospels. It would be nice to visit the core meaning of the bible..Jesus. Just to see what He did on earth and how much love He had for God and for us.