The 3rd eye is the pineal gland, and part of the energy center in your head. You won’t get a book just on that because it’s part of your larger system, and you need to develop your whole system in balance.
If you only concentrate on this only you can become ungrounded and start getting headaches and eye issues. Develop your whole energy body together, it will also be easier to maintain progress as you body will automatically do some balancing for you, and all that energy you put in your head will find it’s way to your other energy storage centers.
When this energy center is developed it’s easier to get psychic impressions. So assuming that’s what you are wanting to do, methods to develop your psychic or astral sense are posted all over the place here on BALG, and you want to look for books with these keywords.
Try these:
And we have free tutorials, some collected here but try the search with refined keywords to get more specific: