Categorising books

Some book bloggers award the books they review marks out of five or ten. Others use a star system. I've always resisted doing this - it seems a bit simplistic - but having racked up a hundred or so reviews I think I have developed a scoring system of my own. It goes a bit like this:

• Brilliant. A classic. Will be read for many decades to come. I don't think any of the books I have read this year fall into this category,but of course some of the "interesting but flawed" books might get promoted after a few years.
• Interesting but flawed. Quite a few of the books I have read and reviewed this year fall into this category, including Will Self's "The Book of Dave", Richard Flanagan's "The Narrow Road to the deep North" and David Mitchell's "The 1000 Autumns of Jacob de Zoet". These are all books that have something interesting to say, and try and look at the art of novel writing with a fresh perspective, but at the same time have weaknesses that are hard to overlook. Over time some of these weaknesses fade, and the reader comes to appreciate the strengths even more. This has happened to me (to a certain extent) with J K Rowling's "The Casual Vacancy", where a bit of perspective has allowed me to appreciate what she was trying to do, and forgive some of the crasser aspects of the novel.
• A dropped ball. A bad book by a good author. For example "Children Act", Ian McEwan; McEwan doesn't stop being a great author by writing a disappointing book, but it's still a disappointing book
• Lionel Asbo. A book with no redeeming features whatsoever - "Lionel Asbo" is the only book in this category, but it deserves one of its own just to emphasise its awfulness
• Why? Books that leave me puzzled as to why the author bothered writing them. Books usually go into this category shortly after I finish them, but often don't stay there, as I slowly (or otherwise) make my mind up about them.
• Dialling it in. A mediocre book by an author who has proven that he or she can write so much better, and where the unavoidable suspicion lingers that the author wasn't trying that hard, or had other things on their mind, such as a possible TV/film adaptation - examples include "How to Build a Girl", Caitlin Moran, "The Black-eyed Blonde" Benjamin Black.
• A guilty pleasure. Books that I ought to be embarassed to enjoy, but which I nevertheless did. Terry Pratchett's work used to be in this category, until I was joined by other adult readers.
• Irritating. "Moab is my Washpot" annoyed me immensely.

More useful than stars or marks out of ten?