Any other book recommendations about more unique maths would be great.
If you're interested in number theory:
"An Adventurer's Guide to Number Theory" by Richard Friedberg is great. I also recommend "Excursions in Number Theory" by C. Stanley Ogilivy and John T. Anderson.
For a great tour of most of modern mathematics, I suggest "Concepts of Modern Mathematics" by Ian Stewart. This is reprint of a book that was originally published in 1975 and revised in 1981. Stewart used the term "Modern" to mean the last 100 years, but I think this book spans a longer period than that. Yes, the book is "old" but I think well-written math books age very slowly.
Finally, not a book but: