Question

It's great of you to give me this book 为什么这样用?

Answer 1

知识点：

It's + adj.of sb to do sth 某人做某事是……的 (侧重人的个性特征)

区别点：

It's + adj.for sb to do sth 做某事对某人是……的（侧重事物本身的属性）

再如：

It's difficulty for him to settle the problem.