We can mark the particular books as S1 & S2.

And the other books as B1, B2, B3, B4, B5, B6, B7, B8.

The particular books are always together.

So, we can arrange this (8 + 1) = 9 books in **9!** way in the shelf **AND** the particular books can itself arranged in **2!** ways.

So, Total ways = **9! * 2!**