There is a variety of reading suggestions here, in no particular order and suitable for different ages and abilities. If you're not sure what is right for you, just ask your teacher for some advice.
Fiction
Robert Harris: Conclave; The Second Sleep
Philip Pulman: Trilogies- His Dark Materials; The Book of Dust
Stephen Fry: Mythos; Heroes
Natasha Solomons: Mr Rosenblum’s List
Nicola Barker: The Cauliflower
Madeline Miller: Circe; The song of Achilles
Michel Faber: The book of strange new things
Charlotte Rogan: The life boat
Catherine Clement: Theo's Odyssey
Keren David: What We're Scared of
Jess Butterworth: Running on the Roof of the World
Irfan Master: A Beautiful Lie
Non-fiction
Roman Krznaric: The Wonderbox; Empathy
Jonathan Sacks: Not in God’s Name
Stephen Fry: The Four Horse Men
Richard Dawkins: River Out of Eden: The God Delusion
Yuval Noah Harari: Sapiens; Homo Deus
Richard Holloway: A Little History of Religion
Daniel Goleman and the Dalai Lama: Destructive Emotions
William Dalrymple: Nine Lives
Patricia Posner: The Pharmacist of Auschwitz
Vardy and Grosch: The Puzzle of Ethics
Leon Leyson: The Boy on the Wooden Box
Nigel Warburton: A Little History of Philosophy
You can also look at his website, www.philosophybites.com to hear podcasts on a variety of philosophical topics.