Google announced yesterday that it had acquired Zagat, one of the most well-known restaurant reviewers. Zagat is best known for its small guidebooks that offer reviews and recommendations on restaurants around the world.

Writing on the company’s official blog, Marissa Mayer, Google’s vice president of Local, Maps and Location Services, wrote, “I’m thrilled that Google has acquired Zagat. Moving forward, Zagat will be a cornerstone of our local offering – delighting people with their impressive array of reviews, ratings and insights, while enabling people everywhere to find extraordinary (and ordinary) experiences around the corner and around the world.”

Zagat was founded back in 1979 by Tim and Nina Zagat, and started as a printed guide to restaurants, with “Zagat Ratings” becoming an industry standard. Recently, however, Zagat has reinvented itself on the web and with mobile apps, bringing itself into competition with the likes of Foursquare. Much of its online content was locked behind a paywall for some time, but Zagat relaunched its website in February to include more free content.

Tim Zagat confirmed on ZAGAT’s website that the couple will remain with the business as co-chairs. “Google is the first place everyone goes when looking for information; it’s the perfect home for our content,” Mr. Zagat said.

While the terms of the deal remain undisclosed, it’s believed that Zagat acquisition is one of Google’s biggest to date in the content business. In 2008 Zagat reportedly put itself up for sale with an asking price of around $200 million, but subsequently took itself off the market, at least until now.