It is actually really difficult to be a book translator and I'm surprised they ever find people to do it. You have to be fluent in the two languages and you have to be creative and artistically inclined, but still willing to try and work with another person's text.
There are so many phrases and words that simply don't work out of the context of a language and you need to be able to find alternatives. It gets even worse if you're translating poetry.
If you are looking for book translation services, I would be very careful to find someone who will be able to do it properly.
In fact, I don't think I'd do it on my own at all. I'd find a publisher willing to give me the details of their translator, or who would work with me to get the book translated.