Although quality is entirely subjective, there are a few things which can make a novel universally crummy. The genre sections of bookstores are paper ghettos full of novels written with very little literary content, character development, or style, hiding behind the facade of the genre and riding by the coattails of good authors in the hopes of making a buck. There are good books in there, books that have been nurtured by their authors with tender loving care, hidden like needles in a pile of needles.
The filler books are usually created with a single thing in mind, to introduce a few imaginitive ideas, to flesh up a plot or to simply capitalize on the thoughts of predecessors. The ideas and the plots presented are often great, but why do you want to read through 200 pages of garbage to get it when that's all the author cared about. He or she could have simply taken all of their novels and expressed the important ideas from each one on a page, thereby offering them without the swamp of styrofoam peanuts. As for the novels written to capitalize on ideas that have already been written out, these are basically fan fiction snapped up by a publisher in the hopes of keeping fans of the earlier works. Ex: Star Wars novels, Star Trek novels, new Dune novels, new Dragonlance novels, etc. etc...not to mention that whenever you look at the shelves now you realize that every damn fantasy, SF story seems to have become a cliffhanger saga. Every time I wander in looking for a good read i'm confronted with "Green Rockmage! Book 27 of the Ewigkeit des Scheisses Saga!" or "Elvenfyre: a Fukhad novel."
One of the heaviest perpetrators in this realm is Kevin J. Anderson, who utterly ruins any universe his pen touches by crayoning all over it with the ideas of a five year-old and the background to match.
These "novelists" give SF and Fantasy a bad name and make it very difficult to pick out a book.
Lo! I have given life to the nodeshell! | 
