How Many Words to Read a Novel?

I really want to read this one novel, but my vocabulary is still very limited. Is translating it slowly an okay way to learn as I go? I could pick up commonly used words quickly and any words I don't know I could find in a dictionary. I'm worried about idioms/colloquialism/expressions and things of that nature though. Honestly, I don't even know where to learn those things anyway (so a good site would be welcome!).

If this would be a horrible approach, let me know. One of the reasons I want to learn Thai is to read books. ^^;