Literal, or, exoteric; is simply the direct and surface level interpretation of something.
Spiritual, or, esoteric; is the hidden meaning.
Mystical; is just the overall tone and genre which something falls into. Sort of like riddles and enigma's which reveal things when properly understood but hide things when not. A good example of this besides the Bible is Greek Mythology. It was a common known fact among ancient Greek philosophers that the mythologies were mystical and esoteric stories that revealed deep truths, but because you had to know this to understand it the common people took them literally. The early Christians spent much time revealing how the philosophers had hidden their truths in the stories they told. They did this so that only the most worthy would understand and the profane who only looked down their whole life would not.
I'll give you one example of thousands in the Bible. In the Gospel of John chapter 6 Jesus tells His followers that "Unless you eat my flesh and drink my blood you have no life in you." When he said this there were hundreds of people listening. They turned to each other and were shocked at what he said. They started thinking he was crazy for demanding weird and impossible things and it said they all left Him except the 12 disciples. Then Jesus looked at them and said "will you go away also?" And Peter said "where will we go?" Then Jesus asked Peter; "who do you say that I am?" Peter replies; "You are the Christ, the Son of the Living God." Jesus responds; "flesh and blood has not revealed this to you Peter but My Father which is in Heaven has revealed this to you. MY WORDS ARE SPIRIT, and those who worship The Father must worship Him in spirit and in Truth."
Now, we can interpret this literally as the Catholics do and say if we don't eat the flesh of Jesus and drink his blood then we are damned. Or, we can understand it to mean what Jesus said it does -- which is; He was speaking Spiritually and the only way a man will have life is if he receives all of Christ and allows Him to come into his heart and mind, search it out, and remove the bad. Christ wasn't saying to literally eat his flesh and drink His blood. He was using spiritual language to teach an eternal Truth. I could give a thousand examples of things like this in the Bible. The Bible even says that men who read the Bible without God's Holy Spirit revealing what it says to them are not going to understand it but it will actually appear foolish to them because their spiritual eyes and ears are closed and they can only see things literally.
I'll leave you with this to prove what I say. This is Jesus Himself speaking.
Mat 13:10 And the disciples came, and said unto him, Why do you speak to the people in parables?
Mat 13:11 He answered and said unto them; because it is given unto you to know the mysteries of the kingdom of heaven, but to them it is not given.
Mat 13:12 For whosoever has, to him shall be given, and he shall have more abundance: but whosoever has not, from him shall be taken away even that which he has.
Mat 13:13 Therefore speak I to them in parables: because they seeing, see not; and hearing, they hear not, neither do they understand.
Mat 13:14 And in them is fulfilled the prophecy of Isaiah, which says; By hearing, you shall hear, and shall not understand; and seeing, you shall see, and shall not perceive:
Mat 13:15 For this people's heart has become gross, and their ears are dull of hearing, and their eyes they have closed; lest at any time they should see with their eyes, and hear with their ears, and should understand with their heart, and should be converted, and I should heal them.
Mat 13:16 But blessed are your eyes, for they see: and your ears, for they hear.
Mat 13:17 For truly I say unto you, That many prophets and righteous men have desired to see those things which you see, and have not seen them; and to hear those things which you hear, and have not heard them.