C语言单链表 看不懂temp-＞next = book； book-＞next =NULL；

//视频45：单链表

/*
    struct Test
    {
		int x;
		int y;
		struct Test *test;//指向自身的结构;
	};
*/

/*
单链表：信息域指针域->

*/


#include
#include

struct Book
{
	char title[128];//书名
	char author[40];//作者
	struct Book *next;
	 //到此完成单链表节点的声明

	//插入节点 头插法

};
	//void getInput(struct Book *book);
	//void addBook(struct Book **library);
	//void printLibrary(struct Book *library);
	//void releaseLibrary(struct Book **library);

//输入书籍信息
void getInput(struct Book *book)
{   //传入一个结构体指针
	printf("请输入书名：");
	scanf("%s",book->title);
	printf("请输入作者：");
	scanf("%s",book->author);
}

//增加书籍
void addBook(struct Book **library)
{   //修改library进行两层解引用
	struct Book *book, *temp;
book = (struct  Book *)malloc(sizeof(struct Book));
	//在堆里面申请一个新的节点
	if(book == NULL)
	{
		printf("内存分配失败了！\n");
		exit(1);
	}
	//调用getInput填充内容
	getInput(book);//传进book的地址
	if(*library != NULL)
	{
		temp =*library;
	//定位单链表的尾部位置
	while( temp->next !=NULL )
	{
		temp = temp->next;
	}
	//插入数据
	temp->next = book;
	book->next =NULL;


	}else{
		*library = book;
		//head执行book节点
		book->next = NULL;
		   //book指向NULL
	}

}

//打印书籍
void printLibrary(struct Book *library)
{
	struct Book *book;
	int count =1;

	book = library;
	while(book !=NULL)
	{
		printf("Book%d:",count);
		printf("书名：%s\t\t",book->title);
		printf("作者：%s\n",book->author);
		book= book->next;
		count++;
	}

}

//释放
void releaseLibrary(struct Book **library)
{
	struct Book *temp;
	while( *library !=NULL )
	{
		temp = *library;
		*library = (*library)->next;
		free(temp);
	}
}
int main(void)
{

	struct Book *library = NULL;
	int ch;

	while(1)
	{
		printf("请问是否需要录入书籍信息（Y/N）：");
		do{
			ch = getchar();
		}while(ch!='Y' && ch!='N');

		if(ch == 'Y'){
			addBook(&library);
		}else{
			break;
		}
	}

	printf("请问是否需要打印图书信息(Y/N):");
	do{
			ch = getchar();
		}while(ch!='Y' && ch!='N');

		if(ch == 'Y'){
			printLibrary(library);
		}

		releaseLibrary(&library);

return 0;
}

看不懂addBook最后部分，没有将新增的书籍存ru**library中，为什么还可以打印出来？