webapi.cs

// GET: api/Books/5
[ResponseType(typeof(BookDetailDTO))]
public async Task<IHttpActionResult> GetBook(int id)
{
    var book = await db.Books.Include(b => b.Author).Select(b =>
        new BookDetailDTO()
        {
            Id = b.Id,
            Title = b.Title,
            Year = b.Year,
            Price = b.Price,
            Author = b.Author,
            Genre = b.Genre
        }).SingleOrDefaultAsync(b => b.Id == id);
    if (book == null)
    {
        return NotFound();
    }

    return Ok(book);
}