One thing that’s clear about Google is that they’ve mastered the art of subterfuge.

At a time when leaks about product launches, acquisitions and potential hires are rife, Google resorted to extraordinary measures to ensure that word of its new social network, Google+, did not slip out ahead of Tuesday’s official announcement.

The company reached out to Reuters late on Friday about a special briefing related to some undisclosed YouTube news, even tasking a YouTube PR-man with a curious sartorial style to coordinate the meeting, to complete the red-herring.

So it was surprising to discover a grinning Vic Gundotra, Google’s head of social, and VP of Product Management Bradley Horowitz, in the meeting room at Google’s headquarters.

Clearly we weren’t here to talk about a new YouTube media partnership.

The pair quickly revealed what they had up their sleeve and proceeded to give a tour of a new social networking service that’s been one year in the making.

So what is Google+ like? And why would you want to invest the time and effort to create another social network if you’re already using Facebook and Twitter?

Google is betting that its approach to privacy and extensive controls over who you share information with on the network will set Google Plus apart.

The service revolves around a concept of “circles,” (presumably not the same circles that Dante visited). You can create as many circles as you like, for whatever categories you want: for example family, co-workers or biking friends. Above the circles are a slew of thumbnail images of friends and contacts which Google suggests you might want in your social network. To add a person to one of your groups, drag the name into a circle.

If you decide to remove someone from a circle, you simply drag their image out of the circle, at which point the image will explode into a cloud of smoke – one of several whimsical touches in Google+.

To use Google+ you need to create a Google profile. At the very minimum, Google requires that you use your real name and include a photo. Beyond that, you can furnish the profile with as much, or as little, detail about yourself as you want.

You can control how much of your profile is visible to other folks on the network: your name and occupation for some folks; relationship status for others. Type a person’s name into a box, and you can see what your profile looks like through their eyes.

In a sense, Google+ combines the Facebook and Twitter models of social networking: You can have friends in your social network with whom you share information, and you can also simply follow certain people, say a movie critic who you don’ t know personally, a la Twitter.

Nearly all Google websites, such as its flagship Google.com search engine and the Google maps site, will have a special toolbar running across the top of the page. The toolbar has an icon of your face alongside your name in the top left, to remind you that you are currently logged on to the Google+ network. Click on your name and you can quickly log off the network, or switch to incognito mode.

Google is also weaving video conferencing into social networking with Google+. You can let people in specific circles know that you’re available for a video conference (that you’re available to “hang out” in Google+ parlance) by clicking on a button. Up to ten people can join a video conference.

While social networking is all about real people sharing information, such as interesting news articles and videos, Google believes there’s room for its algorithmic muscle in the social world too. A feature called “Sparks” serves up Web content on various topics, say sports or fashion, which Google’s technology has determined are popular. You can subscribe to categories of interest, or create your own custom category, and you’ll receive links to the latest content in your news feed.

Google is also releasing mobile apps of Google+ for Android smartphones and iPhone, with special features like group messaging and cloud-based photo storage.

Google is referring to its new service as the Google+ Project, to make clear that’s what’s available now is only the first installment of several more features it says it has in the pipeline.

Despite a checkered history in social (see Google Wave, Google Buzz and to some extent Orkut), Google has not given up on trying to conquer the social networking market.

Right now the service is only available as a “field trial” to a limited number of people. Since social networking success depends on critical mass, it seems likely that Google will open the service up to more people sooner rather than later.

So in the coming months we could have a better indication as to whether Google has finally cracked the code for success in the social networking market.

(Screenshots from Google Works)