Input voltage range of OPA551 Op amp
I see the abs max input voltage specified as follows: (V–) – 0.5 (V+) + 0.5. That means you can exceed either supply rail by no more than 0.5V. 

For example, if you are supplying +/- 12V to the amplifier, the abs max input range is 12.5V and -12.5V.  That doesn't mean that the amplifier will meet the datasheet specs in the region outside the recommended operating conditions, but it does mean that you won't damage it.

The input common mode range is specified as (V–) + 2.5 (V+) – 2.5.  So for proper operation as an amplifier you should observe that constraint, which is obviously much different from the abs max rating.