Quick Solution

To solve this puzzle, we'll combine the clues to build the vertical order of the books from top to bottom. Let's use the `>` symbol to mean "is placed above".

1. Combining the Clues

• From the clue "A is placed below E" (E > A) and the clue "D is placed between A and E", we can establish a definite order for these three books:
  E > D > A
• From the clue "B is placed below A" (A > B), we can add B to the bottom of our chain:
  E > D > A > B
• Finally, the clue "C is placed above D" (C > D) tells us that C must be somewhere higher than D in the stack.

2. Determining Who Can Be on Top

- Our current ranking shows that E is above D. The last clue tells us that C is also above D.
- However, the problem does not provide any information to compare the positions of C and E relative to each other.
- This leads to two possible valid scenarios for the complete order:

1. If E is placed above C, the order would be: E > C > D > A > B. In this case, E is on top.
2. If C is placed above E, the order would be: C > E > D > A > B. In this case, C is on top.

Since both of these arrangements are valid based on the given clues, either C or E could be the book on the top.

Final Answer: The book on the top can be C or E.