To produce a mighty book, you must choose a mighty theme.
– Herman Melville

A story without a theme is merely a list of events. Even though the events may be very interesting, moving or even enlightening, without a unifying or dominant idea they will not engage your reader’s attention from beginning to end. AND, choosing a strong theme, will keep you interested and compelled to write.

Here are a few examples of universal themes for Memoir, Fiction and Non-Fiction Writers.
Ambition – getting what you want, stunted by, thwarted
Betrayal – the pain of, in love and friendship
Coming of age  – loss of innocence
Courage – the courage to deal with conflict, lack of, developing, conquering
Discovery – new places, inner meaning, strength, even treasure
Death – how to escape, facing, what happens after, consequences of
Fear – driven by, dealing with, conquering
Freedom – loss of, gaining, handling, fight for
Good versus evil – survival and the triumph of one over the other
Isolation – physical and emotional
Justice – the fight for, injustice, truth versus justice.
Loss – of life, innocence, love, friends, to avoid
Love – love fades, is blind, can overcome all obstacles
Power – the search for, the loss of, what we are willing to exchange for
Prejudice – racism, bigotry, snobbery, dealing with
Security – the loss of, the need for, when security is shattered
Spirituality and God – the struggle to find faith, live without faith, etc.
Survival – man versus nature

If you want to entertain or teach your audience, give them a great theme. Carry that theme from the first page to the last, and they will follow you anywhere.