Any books you'd particularly recommend outside of US/Presidential history?
I always will take opportunities like this question to recommend Charles Emmerson's 2019 book, Crucible: The Long End of the Great War and the Birth of a New World, 1917-1924 (BOOK | KINDLE). I know it'll sound like hyperbole, but I am not exaggerating: it's one of the best books I've ever read, if not the best. It has stayed with me ever since I finished it, largely because of how absolutely riveting Emmerson's writing style is. I don't know if I've ever read a single book that has told so many incredible stories about so many remarkable people and so many fascinating places. And it does so without ever losing its overall focus or confusing the reader. I love this book and every time I see it on one of my bookshelves I get jealous that I can't read it for the first time over-and-over again.
Another book that immediately comes to mind is Lawrence Wright's Going Clear: Scientology, Hollywood, and the Prison of Belief (BOOK | KINDLE), which I'm sure many others would back me up on. I'm a huge fan of all of Lawrence Wright's work, so you can't go wrong with any of his other books, particularly The Looming Tower: Al-Qaeda and the Road to 9/11 (BOOK | KINDLE) and The Terror Years: From Al-Qaeda to the Islamic State (BOOK | KINDLE), both of which are journalism at its very best. And I understand you asked about books that didn't have anything to do with the Presidency, but it would be criminal if I didn't also suggest Wright's excellent history of the 1978 Camp David Accords between Israel and Egypt, Thirteen Days in September: Carter, Begin, and Sadat at Camp David (BOOK | KINDLE). The difficult peace negotiations between President Carter, Israeli Prime Minister Menachem Begin, and Egyptian President Anwar Sadat are detailed so intimately that Wright originally began writing it as a play, and the storytelling remains just as vivid as if it were being performed on a stage.
By no means is that a complete list of suggestions, but those are the first books that came to mind when reading your question. But, seriously, don't hesitate to read Charles Emmerson's Crucible ASAP!!!