Question

email to your friend thank him the book he send you for entrance test

Answer 1

means.... I can't understand what u say

Answer 2

Being an informal communication, you can simply start with your friend's name and followed by greetings.

It is advisable to express your gratitude, for your friend's help through the useful book that he sent for your entrance test.

You must share your experience of going through the book and your result, if already known to you.