Did the ghost of Samuel appear to Saul after his death?

When Saul consulted the witch (medium) of En Dor, was it really the prophet Samuel that appeared?

No. There are several important scriptures to consider before we examine the actual story, recorded in 1 Samuel 28:7-25 [7] Then said Saul unto his servants, Seek me a woman that hath a familiar spirit, that I may go to her, and enquire of her. And his servants said to him, Behold, there is a woman that hath a familiar spirit at Endor.
[8] And Saul disguised himself, and put on other raiment, and he went, and two men with him, and they came to the woman by night: and he said, I pray thee, divine unto me by the familiar spirit, and bring me him up, whom I shall name unto thee.
[9] And the woman said unto him, Behold, thou knowest what Saul hath done, how he hath cut off those that have familiar spirits, and the wizards, out of the land: wherefore then layest thou a snare for my life, to cause me to die?
[10] And Saul sware to her by the LORD, saying, As the LORD liveth, there shall no punishment happen to thee for this thing.
[11] Then said the woman, Whom shall I bring up unto thee? And he said, Bring me up Samuel.
[12] And when the woman saw Samuel, she cried with a loud voice: and the woman spake to Saul, saying, Why hast thou deceived me? for thou art Saul.
[13] And the king said unto her, Be not afraid: for what sawest thou? And the woman said unto Saul, I saw gods ascending out of the earth.
[14] And he said unto her, What form is he of? And she said, An old man cometh up; and he is covered with a mantle. And Saul perceived that it was Samuel, and he stooped with his face to the ground, and bowed himself.
[15] And Samuel said to Saul, Why hast thou disquieted me, to bring me up? And Saul answered, I am sore distressed; for the Philistines make war against me, and God is departed from me, and answereth me no more, neither by prophets, nor by dreams: therefore I have called thee, that thou mayest make known unto me what I shall do.
[16] Then said Samuel, Wherefore then dost thou ask of me, seeing the LORD is departed from thee, and is become thine enemy?
[17] And the LORD hath done to him, as he spake by me: for the LORD hath rent the kingdom out of thine hand, and given it to thy neighbour, even to David:
[18] Because thou obeyedst not the voice of the LORD, nor executedst his fierce wrath upon Amalek, therefore hath the LORD done this thing unto thee this day.
[19] Moreover the LORD will also deliver Israel with thee into the hand of the Philistines: and to morrow shalt thou and thy sons be with me: the LORD also shall deliver the host of Israel into the hand of the Philistines.
[20] Then Saul fell straightway all along on the earth, and was sore afraid, because of the words of Samuel: and there was no strength in him; for he had eaten no bread all the day, nor all the night.
[21] And the woman came unto Saul, and saw that he was sore troubled, and said unto him, Behold, thine handmaid hath obeyed thy voice, and I have put my life in my hand, and have hearkened unto thy words which thou spakest unto me.
[22] Now therefore, I pray thee, hearken thou also unto the voice of thine handmaid, and let me set a morsel of bread before thee; and eat, that thou mayest have strength, when thou goest on thy way.
[23] But he refused, and said, I will not eat. But his servants, together with the woman, compelled him; and he hearkened unto their voice. So he arose from the earth, and sat upon the bed.
[24] And the woman had a fat calf in the house; and she hasted, and killed it, and took flour, and kneaded it, and did bake unleavened bread thereof:
[25] And she brought it before Saul, and before his servants; and they did eat. Then they rose up, and went away that night.

See All.... The first is the verse immediately prior, which informs the reader that "when Saul inquired of the Lord, the Lord did not answer him, either by dreams or by Urim or by the prophets" (1 Samuel 28:6And when Saul enquired of the LORD, the LORD answered him not, neither by dreams, nor by Urim, nor by prophets.
See All...). God was refusing to communicate with Saul through any means, including His prophets. Samuel, even if he had been still alive, would have had nothing to tell Saul. From this we can infer that the "Samuel" who communicated with Saul was not a prophet of God speaking from beyond the grave.

Another important passage is in Ecclesiastes 9:5For the living know that they shall die: but the dead know not any thing, neither have they any more a reward; for the memory of them is forgotten.
See All..., 10, which says plainly that "the living know that they will die; but the dead know nothing...for there is no work or device or knowledge or wisdom in the grave where you are going." When we die, we enter a state the Bible likens to "sleep" (1 Thessalonians 4:13-14 [13] But I would not have you to be ignorant, brethren, concerning them which are asleep, that ye sorrow not, even as others which have no hope.
[14] For if we believe that Jesus died and rose again, even so them also which sleep in Jesus will God bring with him.

See All...), remaining unconscious until the resurrections at or after Christ's return. There is certainly no soul that lives on, able to communicate with the rest of the living.

Knowing this, the entity Saul communicated with could not possibly have been the ghost or spirit of Samuel, or any other human being. That leaves only the spirit realm as a possibility—and given that God had explicitly cut off communication between Himself (and by extension, His angels) and Saul (compare 1 Samuel 13:14But now thy kingdom shall not continue: the LORD hath sought him a man after his own heart, and the LORD hath commanded him to be captain over his people, because thou hast not kept that which the LORD commanded thee.
See All...; 28:6 and Isaiah 59:2But your iniquities have separated between you and your God, and your sins have hid his face from you, that he will not hear.
See All...), we are forced to conclude that the "Samuel" conjured up by the medium of En Dor was a demonic spirit masquerading as God's prophet.

We might ask, "If it was really a demon communicating with Saul, why did it tell him the truth?" (1 Samuel 28:16-19 [16] Then said Samuel, Wherefore then dost thou ask of me, seeing the LORD is departed from thee, and is become thine enemy?
[17] And the LORD hath done to him, as he spake by me: for the LORD hath rent the kingdom out of thine hand, and given it to thy neighbour, even to David:
[18] Because thou obeyedst not the voice of the LORD, nor executedst his fierce wrath upon Amalek, therefore hath the LORD done this thing unto thee this day.
[19] Moreover the LORD will also deliver Israel with thee into the hand of the Philistines: and to morrow shalt thou and thy sons be with me: the LORD also shall deliver the host of Israel into the hand of the Philistines.

See All...; compare 13:9-14; 15:8-9, 26; 31:2-4). We must remember that the primary goal of Satan and his demons is to destroy us. By selectively telling Saul pieces of the truth, the demon posing as Samuel was able to depress him to the point where Saul was no longer able to stand up (1 Samuel 28:20Then Saul fell straightway all along on the earth, and was sore afraid, because of the words of Samuel: and there was no strength in him; for he had eaten no bread all the day, nor all the night.
See All...).

The demon used parts of the truth, while posing as a man of God, to paint a picture of hopelessness. "And no wonder! For Satan himself transforms himself into an angel of light. Therefore it is no great thing if his ministers also transform themselves into ministers of righteousness, whose end will be according to their works" (2 Corinthians 11:14-15 [14] And no marvel; for Satan himself is transformed into an angel of light.
[15] Therefore it is no great thing if his ministers also be transformed as the ministers of righteousness; whose end shall be according to their works.

See All...).