Changing Noun to Adjective using "of"

I believe the answer to your question hinges on whether it's a mass noun or a count noun. You generally can't use "of" to turn a count noun into an adjective phrase.

• "of book" doesn't work because "book" is a count noun.
• "of assistance" works because "assistance" is a mass noun.

There may be exceptions to this, but I'm sure this rule will stand you in good stead, in the vast majority of cases.

The question clearly asks about all nouns, so the answer is clearly no. There will be many exceptions to the transformation you suggest. A person of interest, for example, does not have the same (not to mention exact) meaning as an interesting person.

You can make an "adjective phrase" out of any or almost any noun by putting "of" in front of it, possibly including an article between the "of" and the noun, but exactly what the result means depends on context.

Usually you turn it into a possessive. "The top of the mountain" means the same as "the mountain's top"; "the creator of Stackexchange" means the same as "Stackexchange's creator"; etc.

Other times the construction has its own connotations. Several of your examples fall in this category. "A subject of interest" doesn't mean a subject belonging to "the interest" but rather "an interesting subject". "A man of importance" means "an important man". Etc. As Eduardo alludes to, "A person of interest" does not mean "an interesting person" but rather is a very specific idiom meaning "a person that the police suspect of being involved in a crime but without enough evidence that they feel justified in calling him a suspect". On the other hand, "a subject of interest to me" means "a subject that I am interested in".

By the way, several of your examples don't mean what you seem to think they mean.

"Of help" does not mean "helpful". A native speaker would not say, "This screwdriver was a tool of help" as an alternative to "This screwdriver was a helpful tool." You can say that someone or something was "a source of help", meaning that's where you got your help from, but that's not the same thing as "a helpful source", which means a resource that was of particular value. "Source of help" usually implies emotional support. Like if you said, "Sally was a source of help when I was trying to quit smoking", you most likely mean that she provided encouragment. But "Sally was a helpful source when I was trying to quit smoking" would mean that she gave you information.

A native speaker would not say, "This is a project of problem" to mean that the project is running into many difficulties. He might say "This is a problematic project", or more likely "This project has a lot of problems." I really can't think of a case where you'd say "of problem". You could say "of the problem" to mean "having to do with the problem". Like, "Here is the cause of your problem" means the same as "Here is your problem's cause."

People do occasionally say things like, "This is a book of no use" meaning the same thing as "This is a useless book", or "It was a town of no importance" meaning "It was an unimportant town". The "of X" version here is used to sound more poetic. The usage is pretty rare and should not be considered a routine substitute.