Yes its real and more common than you think. I would guess that you know several couples who do this and you just don't know it yet.
We did it for 5 years. It was the best sex I ever had.
Some of the most decent people swing. Aside from having a wild side in bed, they are just people.
It's really like being in college again. Imagine you are out with a few friends and none of you have had sex in a while so you are hoping to find a great person that you have a spark with. The dynamic is very similar except the friend you are out with is your spouse.
If you have self esteem issues, you are in trouble if you try to swing. Also, people are very choosy so you had better be fairly decent looking.
The biggest problem is when one person in the couple is confronted with the fact that they are very much less attractive then their spouse. It's easy to pretend you are a good match until you have people begging for you and not your wife... or vise versa.
If you are both confident, emotionally stable and like really wild sex... it's a lot of crazy fun! Dangerous as well, but fun.
One more thing. With the couples we met, one of the couple was deplorably bad in bed. The man was usually small and could only last 6-10 minutes or the woman was all frigid.
Usually it was the man who was bad in bed but the woman 'loved' him so she didn't want to full out cheat. It worked great for me. I had a lifetime of sex in those 5 years. Having 3 women at once is really everything a guy would hope for... and then some.