Re: in v/s into
Generally, we use into for movement. [but of course there are exceptions...]
The book is in the room.
The book is into the room.
If you want to use into in your sentence, you need to use a different verb that shows some kind of movement.
The verb is doesn't show any movement, so you can't use into.
The book flew into the book.
She carried the book into the book.
Sometimes in and into are used interchangeably and mean the same thing:
He threw the book in the fire.
He threw the book into the fire.
We must go into this store!
We must go in this store!
Sometimes in and into mean different things in the same sentence:
He drove in the parking lot.
(this means he was already at the parking lot and began to drive around inside of it)
He drove into the parking lot.
(this means he entered the parking lot from the street)
And sometimes in and into cannot be used in the same sentence:
He is going into medicine.
(this means he will study medicine)
He is going in medicine.
Don't walk into that glass door!
(this means do not collide with the door)
Don't walk in that glass door!
Please file these documents in alphabetical order.
Please file these documents into alphabetical order.