Well, they're virtually identical, they convey the same meaning just in two different ways. A particular sitiation might incline you to choose one phrase over the other though.
For example, you've started translating the book and work your way through that. Here you can use both phrases.
If you haven't started translating the book and you just point out that you think the book is difficult to translate, well, you can still use both phrases, but the second one is not really good for this case.
I better rephrase it like that:
Эту книгу трудно перевести.
Something like that. I hope it's of any help