There are authors who are aiming to write a work of art, and others who are, like Christie, craftspeople who know how to make something that works well. Whatever you may think of her style, she found a formula that appealed to a lot of readers, perhaps because it offered a small mental challenge; the "hook" of "who dunnit". Catherine Cookson and Agatha Christie's books exploit the desire of some readers to know what they are getting; if you buy one of their books you know exactly what it will be like in terms of both plot and character - and you know they won't be *too* challenging - or violent, or scary. This makes them a "safe bet" for a holiday read. Christie's books are now popular for being things of their time; the period details which once made them contemporary now lend them an old-fashioned charm. That said, I haven't read them since I was a teenager either!