The S&P/Case Shiller 20-city composite home price index fell a seasonally adjusted 0.5 percent in July, the third straight month of declines.

When you combine that with recent decreases in existing and pending home sales, "there is a sign of some weakening" in the housing market, though it's "not dramatic," Nobel laureate economist Robert Shiller, whom the index is named after, told CNBC.

Existing home sales dropped 1.8 percent in August, and pending home sales slid 1 percent.

So it now a good time to buy a home?

"If it doesn't go down, it might be an ok investment," Shiller said. "We are living in a world of disappointing investments. I say the same thing about the stock market. It's overpriced, [yet] it's not a bad investment all things considered."

And why is the stock market overvalued?

The economy's recovery and the Federal Reserve's stimulus explain some of it, Shiller said. Also, "it's something about anxiety," he stated.

There's anxiety about geopolitical turmoil, income inequality and job losses, Shiller noted. "You might think stock markets should go down when people are anxious," he explained. But, "it creates a desire to save more."

Many analysts have mixed views about housing.

"In order to support further gains in home prices, you would need stronger housing demand, an improvement in the rate of household formation, and inventory levels to remain lean," Michael Gapen, a senior U.S. economist for Barclays Capital, told Bloomberg.

"You will get all of this, it will just be at a moderate pace."

Related Stories:

• Financial Times: Income Inequality Is Suppressing the Housing Market
• Wondering About the Weak Housing Market? Look At Education