Geometry

Question Analysis  
This question involves arranging items with a restriction (two books must stay together).  

Key Concept Explanation  
When two items must stay together, treat them as a single unit.
Then, calculate permutations for the total units and multiply by the permutations within the grouped items.  

Step-by-Step Solution  
1. Treat the two books as one combined book. Now, we have: 1 (combined book) + 3 (other books) = 4 units.  
2. The number of ways to arrange these 4 units is 4! = 4 x 3 x 2 x 1 = 24.  
3. The two grouped books can switch places (2! = 2).  
4. Total permutations:  

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