from fastapi import APIRouter, HTTPException
import uuid

books = []  # In-memory storage

router = APIRouter()

# Book Model
class Book:
    def __init__(self, title, author, description):
        self.id = str(uuid.uuid4())
        self.title = title
        self.author = author
        self.description = description

# Book Schema

@router.post("/booknies")
async def create_book(book: BookSchema):
    """Create a new book"""
    if any(b.title == book.title for b in books):
        raise HTTPException(status_code=400, detail="Book already exists")

    new_book = Book(book.title, book.author, book.description)
    books.append(new_book.__dict__)

    return {
        "message": "Book created successfully",
        "book_id": new_book.id,
        "title": new_book.title,
        "author": new_book.author,
        "description": new_book.description
    }
```

This code defines a POST endpoint `/booknies` that creates a new book in the in-memory `books` list. It includes a `Book` model class to represent a book, and a `BookSchema` Pydantic model for data validation. The endpoint checks if a book with the same title already exists, and if not, creates a new `Book` instance and appends it to the `books` list. The response includes the details of the newly created book.