A few suggestions you can look into:
•Mathematics: A Very Short Introduction, Timothy Gowers
• The Millennium Problems: The Seven Greatest Unsolved Mathematical Puzzles of Our Time
by Keith Devlin
•The Mathematical Century: The 30 Greatest Problems of the Last 100 Years, Piergiorgio
• The Calculus Gallery, William Dunham
• Letters to a Young Mathematician, Ian Stewart
• The Book of Numbers byJohn H. Conway
•Fermat’s Enigma: The Epic Quest to Solve the World’s Greatest Mathematical Problem, Simon Singh
•101 Careers in Mathematics, AndrewSterrett
•The Best Writing on Mathematics Series