I find writing reviews pretty hard - whether I like a book or not. That is because it is sometimes hard to recall WHY you like or dislike something. It's easy to summarize, but hard to explain.
For instance, I liked Darkvision, but reading my review of it, I listed quite a bit of criticism. It is likely because that is easier to write. I can explain why I didn't like the villain (I am pretty sure I made that clear), but it is harderÂ to explain why I enjoyed reading about the heroes.
Inconsistencies, things I miss, and things that annoy are easy to target, including elements that are a matter of taste. They are all easier to remember as well.
It may help to try and find why certain events occur in a novel, and in what manner elements that you like or dislike impact the story. For instance, when a novels' action isÂ focused on the heroes, and makes you sympathise with them, having a less interesting villain is not a big issue: it merely makes you want the good guys to win even more. That is not a bad thing - it seems better than rooting for a villain you know will get butchered :P
One thing you may also consider is expectations. What you expect may impact how you view the novel. I know for instance, that reading Maiden of Pain (which I liked as it gave the perspective of a priestess of Loviatar) gave me unrealitic expectations of Lady of Poison (which doesn't do that). That colored my opinion and made the negatives I found weigh harder.
If you are aware of these expectations, it is only fair to inform your reader.
Finally, sometimes you cans ee what the intent was - it just didn't work out for you. Listing the (perceived) intent may help put readers see things form more than the criticism view. For instance, I did not like the Knight of Myth Drannor series. I could see (I think) what Ed tried to do: paint a complex net of intrigue and scheming, in the background of a struggling bunch of heroes who get accidentally involved. For me, that didn't work, as it led to much confusion and too many coincidences and dead ends. But I could see how Ed's mind was (possibly) workingÂ (and ironically, it is the way my mind works, too).
All that does not necessarily lessen the criticism you have. It may, however, paint a context that may help readers judge whether your gripes are something they would have quarrel with.
Finally, try not to dissuade people from reading the novel. Your taste may not be mine. "Avoid this at all cost' is not something you should put in a review.
In the end, even 'bad' novels should be read - after all, it is much more fun to gripe together
Oh - and spell check your review.