Dear All,
It's often quite easy to tell a bad/undeveloped/cliche story by gut-feeling, but just to elaborate a bit more:
1) It is often said that authors are eccentric people, and I guess this makes a certain amount of sense as originality is, after all, somewhat the equavalence of eccentricity in a good way. For a story to be good, it really has to be enjoyable throughout, and does not fume with hints of "copy-cat" or cliches all the way. I personally think that fantasies and science fictions have reach a peak these days, where the new stories coming out now are often the depiction of very used-up topics- and this is especially severe, because of all the fandoms going around. In other words, you see a boy with magic powers or "this is an elfin world" all the time.
2) Continuing from above, the product of fandom is often not only unoriginal, but very low in quality, because they are often written by fans who squeal at "hawt guys" for fans who squeal at "hawt guys". In more generla terms, they do not mimic, or even attempt to mimic, the real world or at least a similar logical sequence, but are simply stories that want to rush to the kissing part fast- as someone put it on a certian previous post.
3) To be a good book, the author really has to be original, and able to justify all the events/concepts that appear in his/her novel.
4) And, of course, using good or at least classy/stylish English is quite essential.
-Puayen