What I find in most of the books I read. "People are all alike". No matter the genre, year or social status or wealth. There is that common thread.

yoyo, do you mean an 'epiphany' in the sense of a manifestation of a supernatural divine reality or a moment of great or sudden revelation? (both quotes taken from the huge Collins English dictionary).
I can't think of any particular book off-hand, perhaps because the stuff I read isn't 'deep' enough, or often comes into the bio/auto bio/dull text-book class.
As ladyrose mentions I have certainly found that from my historical reading (and I don't mean 'romances' and other modern novels looking back into the past) we are certainly little different from our ancestors . . . but just covered with a thin veneer of civilisation ;-)
What about an eg from you?

Veer,
What I meant was an insight which had not occurred to you before you read the idea in that context. Or perhaps the idea was suddenly made clearer and more personal by the author's interpretation of it.

There are books which, as I was reading them, suddenly offered me an insight into a problem that I was facing in my life.
It gave me another way of looking at it perhaps.

To me, an epiphany is a thought which seems to come out of the blue and brings you a deeper understanding of or a new view of a particular situation.

Psycho-Cybernetics by Maxwell Maltz helped me at a low point in my life. From the Amazon review: "Happiness and success are habits. So are failure and misery. But negative habits can be changed--and Psycho-Cybernetics shows you how!"

I gave my original copy away to someone I thought it would benefit and later bought another for myself and re-read it. Both readings helped me, and I am not much of a self-help-book type of person.

A KInd of Loving by Stan Barstow

I loved that man and that book, and now he's dead.

The summer before 8th grade I was out boating on Fort Loudon Lake with cousins when I had an epiphany that there was nothing new under the sun. Discouraging because my great insight was unique and the end of my intellectual life, because, after all, what other original idea could I ever have? Then that fall we covered the Transcendentalists and I read Emerson who elegantly and pithily stated the same concept. To find out at 13 that Emerson had beat me to my one great idea by a hundred years....

Maybe my other epiphany came from reading a Daniel Webster speech. In 1848 he said he wouldn't vote one penny toward the development of the West because it would never be of any damn use to anyone. That was months before gold was discovered at Sutter's Mill. I discovered that very smart people could be completely wrong.

Not so many epiphanies as an adult.