from fastapi import APIRouter, HTTPException
from pydantic import BaseModel, Field
from typing import Optional

router = APIRouter()

# In-memory storage
books = []

    class Config:
        schema_extra = {
            "example": {
                "title": "Book Title",
                "author": "Author Name",
                "description": "Book description",
                "rating": 4
            }
        }

@router.post("/book", response_model=BookModel)
async def create_book(book: BookModel):
    """Create a new book"""
    if request.method != "POST":
        raise HTTPException(status_code=405, detail="Method Not Allowed")

    book.id = len(books) + 1
    books.append(book)

    return {
        "method": "POST",
        "_verb": "post",
        **book.dict()
    }
```

This code defines a `BookModel` using Pydantic, which includes validation rules for each field. The `create_book` endpoint accepts a `BookModel` instance in the request body, assigns a new `id`, appends it to the `books` list, and returns the created book object along with the HTTP method metadata.