Sure! Here are the rewritten sentences:

1. What an interesting book!
=> How **fascinating**!

2. We will have a vacation that lasts for three months.
=> We will have a **three-month vacation**.

3. The children couldn't go swimming because the water was very cold.
=> The cold water prevented **the children from swimming**.

4. How thick is that novel?
=> What **is the thickness of that novel**?

5. He got to London by taxi last Monday.
=> He took **a taxi to London** last Monday.

6. It will not be necessary for you to go to the meeting next week.
=> You won't **have to attend the meeting** next week.

7. Lan found driving on the left difficult.
=> Lan wasn't used **to driving on the left**.

8. How high is Mount Everest?
=> What **is the height of Mount Everest**?

9. How much is a bottle of water?
=> What **is the price of a bottle of water**?

10. Let's dance and sing a song.
=> What about **dancing and singing a song**?

11. This building belongs to my brother.
=> This is **my brother's building**.

12. Can I help you?
=> What **can I assist you with**?

Feel free to ask if you need further assistance!