The story about the fall of Adam is found in Genesis 3.
The first thing to note is that Adam was created by God Himself, directly. He was not born of a woman and man. He had the most intimate relationship of any man, save Jesus His son and the Christ. Adam was the first man to experience the ramifications of choice, Angels already had this experience.
We know this because Angels were already created before the foundations of the Earth were laid, which are all the things needed to sustain life before God created man or other creatures and placed them on the earth. (Job 38) The fall of Lucifer took place before these foundations were laid.
God created free will and choices, God Himself even created evil in order to perfect Angels and mankind.
Isaiah 45:7
7 I form the light, and create darkness: I make peace, and create evil: I the Lord do all these things.
This is not to say that God decided what Angels or who in mankind would chose to partake of the evil, but the they could. There is a purpose in it, if there were no choice, there is no perfecting of mankind, we would be merely robots.
The challenge with Adam, was that he knew the heart of God and Gods intentions, he understood what he was doing and the extent of the wrong, which plummeted mankind into a sinful nature as a whole.
1 Timothy 2:14
14 And Adam was not deceived, but the woman being deceived was in the transgression.
The key element in the Genesis 3 passage is not the fruit aspect itself, but the prohibition against eating it. God gave Adam and Eve only one prohibition in His instructions. Whether there was some spiritual property within the fruit is really irrelevant.
The sin was in disobeying God's command. By eating the fruit (an act of disobedience), Adam and Eve gained personal knowledge of evil. They already knew good, but now they had the contrasting experience of the evil of disobedience and the guilt and shame that came with it.
Satan's lie was that knowing good and evil would make them like gods (Genesis 3:5). In reality, they were already made in the image of God and had the blessing of His good pleasure.
The lesson for us today is that when God prohibits something, it is for our own good. Disobeying Him, going our own way, or deciding for ourselves what is and is not beneficial to us will always lead to disaster.
God created us and knows what is best for us, and when He prohibits something, we should listen to Him. When we choose to obey our own wills instead of His will for us, things never go well for us.
Adam and Eve made that discovery after eating the forbidden fruit, and mankind has suffered the consequences of their decision ever since.
Romans 5:12
12 Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned:
The fall of Adam and therefore mankind was ordained from the beginning, man has to be perfected by our choices. This is a broader issue that surround the release of Satan after the thousand year reign and his deception of Christians after the fact.
Revelation 20:7-10
7 And when the thousand years are expired, Satan shall be loosed out of his prison,
8 And shall go out to deceive the nations which are in the four quarters of the earth, Gog, and Magog, to gather them together to battle: the number of whom is as the sand of the sea.
9 And they went up on the breadth of the earth, and compassed the camp of the saints about, and the beloved city: and fire came down from God out of heaven, and devoured them.
10 And the devil that deceived them was cast into the lake of fire and brimstone, where the beast and the false prophet are, and shall be tormented day and night for ever and ever.
Christians have to transition from faith to fact, from what you believe to what you know, which is the predicate for going to Heaven in the first place. To see Heaven, Jesus on the Throne etc. Once you have experienced all this, you know and faith is no longer part of the equation.
In this regard the perfecting of man and his choices become sacrosanct with our salvation, to become like the Angels knowing the fullness of what God has said through physical experience, that way if your deceived as the Angels were, you deserve your fate.
Acts 2:23 - God knew in advance man would fall and need a Savior
23 Him, being delivered by the determinate counsel and foreknowledge of God, ye have taken, and by wicked hands have crucified and slain:
A third of the Angels fell into sin as well because they have the same free will and choices. When God created choice, He did so before He created man.
Isaiah 14:12-16 - Sin was found in Lucifer while he was in Heaven
12 How art thou fallen from heaven, O Lucifer, son of the morning! how art thou cut down to the ground, which didst weaken the nations!
13 For thou hast said in thine heart, I will ascend into heaven, I will exalt my throne above the stars of God: I will sit also upon the mount of the congregation, in the sides of the north:
14 I will ascend above the heights of the clouds; I will be like the most High.
15 Yet thou shalt be brought down to hell, to the sides of the pit.
16 They that see thee shall narrowly look upon thee, and consider thee, saying, Is this the man that made the earth to tremble, that did shake kingdoms;
Ezekiel 28:13–19 - The vanity of Satan was found in him while in Heaven
13 Thou hast been in Eden the garden of God; every precious stone was thy covering, the sardius, topaz, and the diamond, the beryl, the onyx, and the jasper, the sapphire, the emerald, and the carbuncle, and gold: the workmanship of thy tabrets and of thy pipes was prepared in thee in the day that thou wast created.
14 Thou art the anointed cherub that covereth; and I have set thee so: thou wast upon the holy mountain of God; thou hast walked up and down in the midst of the stones of fire.
15 Thou wast perfect in thy ways from the day that thou wast created, till iniquity was found in thee.
16 By the multitude of thy merchandise they have filled the midst of thee with violence, and thou hast sinned: therefore I will cast thee as profane out of the mountain of God: and I will destroy thee, O covering cherub, from the midst of the stones of fire.
17 Thine heart was lifted up because of thy beauty, thou hast corrupted thy wisdom by reason of thy brightness: I will cast thee to the ground, I will lay thee before kings, that they may behold thee.
18 Thou hast defiled thy sanctuaries by the multitude of thine iniquities, by the iniquity of thy traffick; therefore will I bring forth a fire from the midst of thee, it shall devour thee, and I will bring thee to ashes upon the earth in the sight of all them that behold thee.
19 All they that know thee among the people shall be astonished at thee: thou shalt be a terror, and never shalt thou be any more.
Revelation 12:4 - third of the angels fell with Satan
4 And his tail drew the third part of the stars of heaven, and did cast them to the earth: and the dragon stood before the woman which was ready to be delivered, for to devour her child as soon as it was born.
Revelation 12:7–9 - The war in Heaven
7 And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels,
8 And prevailed not; neither was their place found any more in heaven.
9 And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.
The point of all this choice is that we would never know grace if we had never needed grace. Therefore, all of God’s plans—including the fall, election, redemption, and atonement of mankind serves the purpose of glorifying God.
God ordains future events in such a way that our freedom and the working of secondary causes (e.g., laws of nature) are preserved. Theologians call this “concurrence.” God’s sovereign will flows concurrently with our free choices in such a way that our free choices always result in the carrying out of God’s will (by “free” we mean that our choices themselves, are not coerced by outside influences).
God foresaw Adam and Eve’s fall. He created them anyway in His own image, to bring glory to Himself. They were given freedom to make choices. Even though they chose to disobey, their choice became the means by which God’s ultimate will was carried out and by which His full glory will be seen in the end.