As a young girl, author Amy Tan asked her mother, who was both vain and beautiful, if she was also beautiful. Tan's mother looked her over, then said, "No. You're just average."

"Then she said it was good that I was not beautiful because eventually I would lose that beauty," Tan tells us. "If I was beautiful, everyone would judge me based on that and never know who I was. I could lose myself once I lost my beauty."

Tan's childhood lessons about beauty have served her as a bestselling author. "Those lessons apply to my writing today," Tan says. "If you land [number one] on a list, that number can only go down. It's a reality. If you see yourself through a number, you're going to be disappointed because at some point that number will change. So I let my publishers worry about the numbers. That was a very valuable lesson that my mother thought me."

While writing her latest book, The Valley of Amazement, Tan examined more mother-daughter lessons from her childhood. She was already working on another novel but was waylaid when she saw an old photograph of Chinese courtesans. Tan was struck because a family photo showed her grandmother as a young woman, in the same dress and pose as the courtesans.

The photo sparked an idea in Tan: Was her grandmother the chaste, conservative young woman her family thought she was, or was she something else? "With my grandmother, I never would have imagined anything like that. What I had been told had been so far removed from that. I was told she was a traditional, quiet, old-fashioned woman with very few words to say. I started doing research, what was the real story of her life? Why did she marry so late? People said it was because her parents loved her too much, they just adored her and they didn't want her to get married, they wanted her to just live at home with them. That just didn't sound right."

Tan's grandmother eventually did get married, but exactly how that happened was unclear.

Apparently she met a man one day "and he fell in love with her so he tried to rape her ... In one version, he had a knife to her throat and said, 'If you don't marry me, I'll kill you.' And then in another version, he had the knife to his own throat and said, 'If you don't marry me, I'll kill myself.' Why was there a knife in that story? That unleashed all these questions. I wanted to know what was true and what wasn't.

"And in [trying to] finding that out, I looked at my mother and myself and tried to figure out what characteristics we had received from my grandmother. If she had been a courtesan, what did she have to do to keep a sense of self? I look back at the advice my mother gave me [about beauty] and realized that would have made sense coming from a woman who might have been in that profession."

Tan is careful to to say "might have been" when discussing her grandmother's possible profession. "I can't say that she definitely was a courtesan, but so much of what I had been told turned out not to be true."

After exploring her grandmother's history, Tan crafted The Valley of Amazement, an epic story of two Chinese women separated by time and place and their search for self-identity. She appears at the Asia Society Texas Center to discuss the novel as part of the center's Books in Conversation series.

Books in Conversation: Amy Tan, The Valley of Amazement starts at 7 p.m. on Monday. Asia Society Texas Center, 1307 Southmore. For information, call 713-496-9901 or visit asiasociety.org. $35.