HI,

If you like non-fiction, I recommend "Breaking NIght" by Liz Murray.

First, I watched the YOUTube video "Homeless to Harvard". This book is her autobiography.

By this book I firstly knew about poor white. She was born between drug addicted parents.

She spent the nights at her friends' homes  hiding from their parents attention. In those situation

she studied hard, staying positive and got the scholarship of New York Times for Harvard. So impressive.

It's hard to judge difficulty for an English learner. I've been reading a Kurt Vonnegut novel (Galápagos, not one of his best) and thinking that he writes in fairly straightforward English. You might try Slaughterhouse-Five and see whether his dark humor appeals to you.

Like Cara, I, too, like Alexander McCall Smith but am not sure about difficulty. Nor am I sure a foreign speaker would pick up on the "tone of voice" and the turns of phrase used e.g. by Mma Romotswe and the other character in the First Ladies' Detective Agency series so I might go to far as to suggest 44 Scotland Street and its (many) successors.