There are some words that can be used as one word or two — and it does make a difference which you choose. These words include everyone (every one), anyone (any one), sometimes (some time or some times), and into, our culprit for today. I talk about these words in Correct Me If I’m Wrong.
I turned my book into the library. Well, unless you are a magician you probably can’t really turn your book into an entire library! However, you can turn your book in to the library — thus, not having to pay any overdue fines!
I turned my car into the garage. Again, magic ability required. This is an easy mistake to make, something you can gloss right over — as may your reader, but you might as well get it right.
In the case of into versus in to, in the above examples, in actually goes with the verb turn; to is the preposition in the phrase to the library or to the garage.
which should one say “can the patient book in to see me” or “can the patient book into see me”?
I have not used that phrase, but I would definitely say in to as two separate words.