void insert_book(struct book *head, struct book *new_book, int position)：在链表的指定位置插入一个新的图书。

好的，下面是一个示例代码实现在链表的指定位置插入一个新的图书：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// 定义一个图书结构体
struct book {
    char title[50];
    char author[50];
    int pages;
    int year;
    struct book *next;
};

// 在链表的指定位置插入一个新的图书
void insert_book(struct book *head, struct book *new_book, int position) {
    struct book *current_node = head;
    int count = 0;
    while (current_node != NULL && count < position-1) {
        current_node = current_node->next;
        count++;
    }
    if (current_node == NULL || count != position-1) {
        printf("Invalid position!\n");
        return;
    }
    new_book->next = current_node->next;
    current_node->next = new_book;
}

// 打印链表中的所有节点
void print_book_list(struct book *head) {
    struct book *current_node = head;
    while (current_node != NULL) {
        printf("%s, written by %s, %d pages, published in %d\n", current_node->title, current_node->author, current_node->pages, current_node->year);
        current_node = current_node->next;
    }
}

int main() {
    // 创建链表
    struct book *head = NULL;
    struct book *book1 = (struct book *)malloc(sizeof(struct book));
    strncpy(book1->title, "The Great Gatsby", 50);
    strncpy(book1->author, "F. Scott Fitzgerald", 50);
    book1->pages = 180;
    book1->year = 1925;
    book1->next = NULL;
    head = book1;
    struct book *book2 = (struct book *)malloc(sizeof(struct book));
    strncpy(book2->title, "To Kill a Mockingbird", 50);
    strncpy(book2->author, "Harper Lee", 50);
    book2->pages = 281;
    book2->year = 1960;
    book2->next = NULL;
    book1->next = book2;
    struct book *book3 = (struct book *)malloc(sizeof(struct book));
    strncpy(book3->title, "1984", 50);
    strncpy(book3->author, "George Orwell", 50);
    book3->pages = 328;
    book3->year = 1949;
    book3->next = NULL;
    book2->next = book3;
    printf("Book list:\n");
    print_book_list(head);
    // 插入新图书
    printf("\nInsert a new book:\n");
    struct book *new_book = (struct book *)malloc(sizeof(struct book));
    printf("Title: ");
    scanf("%s", new_book->title);
    printf("Author: ");
    scanf("%s", new_book->author);
    printf("Pages: ");
    scanf("%d", &new_book->pages);
    printf("Year: ");
    scanf("%d", &new_book->year);
    int position;
    printf("Insert position: ");
    scanf("%d", &position);
    insert_book(head, new_book, position);
    printf("\nBook list after insertion:\n");
    print_book_list(head);
    return 0;
}

这个程序首先创建了一个包含3个图书的链表，然后要求你输入一个新的图书的信息和插入的位置，最后将新的图书插入到指定的位置，并打印出链表中的所有图书。如果插入位置不合法，则会打印出错误信息。你可以根据自己的需要修改图书结构体的成员或者增加新的成员。