Commercial vs. literary fiction

I've been reading a lot of fiction, aiming for decent stuff but ending up with a mix. Trying to figure out the line between commercial and literary fiction. I think it might be one of those nebulous things like the point at which dusk turns to darkness.

Recent titles have included White Oleander by Janet Fitch, The Secret Life of Bees by Sue Monk Kidd, Anne's House of Dreams (a Green Gables sequel) by Lucy Maud Montgomery, The Solitude of Prime Numbers by Paolo Giordano, Madame Bovary by Gustave Flaubert (still reading), Vinegar Hill by A. Manette Ansay, and Message in a Bottle by Nicholas Sparks.

Obviously Sparks' work falls under the commercial category, and the quality reflects it. (No offense Nicholas.) He's got a knack for coming up with compelling story concepts, but the writing itself is a bit weak, and the character development is shallow.

But what about The Secret Life of Bees? Where does that fall on the spectrum?