I think you need to separate personal liking from technical skill. Personally there are far more people, that like to have a poster of some pin-up girl on their wall, but that does not keep them from accepting that the "Mona Lisa" is a great picture, and that the artist were able to do an technical good painting on one side, while being able to carry smalles hints of emotion from his model into the picture as well.
So someone saying, that he thinks a certain authors wirting style is "dry as the sun" does not automatically keep you from accepting if something is done in general well.
I have my troubles as example with the famous bookwriter Dostojewski. I am able to recognize, that he manages to make the people in his book truly alive to the readers, their feelings, emotions, causes to act, ... As well that reading his books really lets you "spawn" into the time of the time of the old russian empire and gives you a great impression of how people lived around that time, what troubled them, what reasons caused them to think as it was normal for that time...
But reading his books is for me like trying to eat overcooked, wetty, oily spaghetti with a single chinese chopstick. So there are only two books, that I ever stopped reading in the middle of it, but one of Dostojewskis was one of it. -.- Even when I really would have liked to known how the story and plot goes on. The characters are well, the plot is well, the story is done well, the topic is interesting... its simply the personal authors way of writing it down and forming sentences that personally annoys. But personally disliking a writing style, that has no real technical flaws in it, does not make a book bad, its simply causes that writing style to be personally disliked by one. ^^
An example for an "bad book" would be: Characters without background, that are bad out of wanting to be bad and that are good out of wanting to be good, characters acting in certain ways, not out of reasons, but simply to get the plot on, an plot that matches an episode of an kids cartoon series... ^^ To give you an example, one of the stuff why I never managed to get into the Pokemon series, was simply that I missed the reason to be motivated to play it. So I am Ash and I do my journey, because I need to become the greatest pokemon master of them all. Ok, WHY do I need to become that? What exactly will happen horrible, if I dont manage to become that? Why is it so important for him to prove himself, to be better and being able to beat people, that have never done anything to him? ... O_o Until now I never had to treat to go to my neighbor and battle him, out of no reason, only to prove myself that I am stronger then my neighbor. So why is this boy doing this? O_o