Lots of good suggestions here. I’ve read most of all of McCullough stuff. For in depth history he is amazing. If you like history, Doris Kearns Goodwin has great options including Team of Rivals(Lincoln); Ron Chernow(Alexander Hamilton); Civil War buffs should look at Jeff Shara.
For fiction, 2 of my Favorites are Shantaram by David Roberts ( Bombay ) and Trinity by Leon Uris( Ireland) for amazing character development and cultural drama. For lighter stuff, anything by Michael Creighton ( JURASIC) or Dan Brown (Davinci Code) is a good bet.