My husband had a versectomy 10 years ago and I have just found out I am pregnant, is this for real?

Yes, it is for real. If you consult any urologist or do any research online regarding the effectiveness of a vasectomy, there is roughly a .0000000001 chance of failure, resulting in possible pregnancy. Although a vasectomy is as effective a means of birth control as there can be outside of altogether abstaining from sexual relations, it's still not 100%.

Well if you're pregnant, it's definitely for real.

While the success rate is usually high with a vasectomy there is a 1% chance that the procedure can fail.

Usually there are 2 main reasons.

The first is usually shortly after the procedure when there is still some residual sperm left thus the woman gets pregnant.

The other is usually after 12 months. The vas deferns grows back together, thus the procedure has failed.

Between 2-5 years after the initial vasectomy 11 of 1,000 procedures usually fail.

Here is a site that tells you more what exactly may have happened...
Pregnancy After Vasectomy