from fastapi import APIRouter, HTTPException
import uuid

books = []  # In-memory storage

router = APIRouter()

@router.post("/books")
async def create_book(
    title: str,
    author: str,
    description: str = None
):
    """Create a new book"""
    if request.method != "POST":
        raise HTTPException(status_code=405, detail="Method Not Allowed")

    book_id = str(uuid.uuid4())
    books.append({
        "id": book_id,
        "title": title,
        "author": author,
        "description": description
    })

    return {
        "message": "Book created successfully",
        "book_id": book_id,
        "method": "POST",
        "_verb": "post"
    }
```

This code defines a POST endpoint at `/books` that creates a new book entry in an in-memory list called `books`. It takes the `title` and `author` as required parameters, and an optional `description`. It generates a unique `book_id` using `uuid.uuid4()` and appends a new dictionary to the `books` list with the provided data. The response includes a success message, the generated `book_id`, and the expected `method` and `_verb` fields.