Harry Potter and a new flat-rate annual shipping plan are enchanting Amazon.com’s performance on Wall Street.

Shares in the online retail giant hit their highest level since 2000 yesterday, reaching $88.80 in mid-day trading on the heels of strong results in the company’s second-quarter earnings.

The stock ended the day up 24 percent, or $16.93, to $86.18.

Net sales for the quarter increased 35 percent to $2.89 billion, while net income more than tripled to $78 million.

Particularly strong was the company’s North American sales, which grew 38 percent year-over-year to $1.6 billion.

Harry Potter mania helped draw increased traffic to the Web site. Amazon received more than 2.2 million pre-orders of “Harry Potter and the Deathly Hallows” worldwide ahead of the book’s July 21 release.

Also aiding business was the growing popularity of Amazon Prime, a new service that enables customers get unlimited, express two-day shipping for an annual flat fee of $79 per year.

“Fast delivery, which includes Prime, is a big deal for us,” Amazon CFO Tom Szkutak said. “It’s certainly having an impact on our overall growth rate.”