Help~!!

[Flyby]

I don't know the difference between these two sentences.

a. This book has been loved by many people.

b. This book has been being loved by many people.

 

[Dawood Usmani]

I don't know the difference between these two sentences.

a. This book has been loved by many people.

b. This book has been being loved by many people.

The first one is ok but the second is obsolete. This is seen in some old grammar books only for practice which I think is useless. For what's the use of learning things that are not in use.
Hope this helps.
Regards!
Dawood