Quote Originally Posted by impulse View Post
Эта книга трудна для перевода VS Эту книгу трудно переводить

I think the first one means,

The book is difficult for translations. In that sentences the sort form of the adjective which is refers to the book.
- right!

Quote Originally Posted by impulse View Post
And the second exaplme means,

It is difficult to translate that book (I changed the word order to indicate i want to refer to the noun) So here the adjective refers to the verb.
- hmm...not exactly. It rather refers to the "dummy" subject which is expressed by "it" in English (It is difficult), and which is just omitted in Russian.

You can simplify the phrase to make it clearer:
Мне трудно. - It is difficult to me.
Это очень трудно. - That (something mentioned before) is very difficult.
It is the same as when you say:
Мне холодно. - It is cold to me.
Сегодня жарко. - It is hot today.
Здесь весело. - It is joyfully here (meaning that people are having lots of fun).
Скучно. - It is boring.

To be precise, they are not even adjectives. Neither they are adverbs. The words in those examples (ending with "-о") look like adverbs (or like neuter short adjectives), but according to the academic grammar they are "words of condition" here. They are used when you describe a condition which just exists, and normally no grammatical subject is needed.