Finally thought of a good Riley riddle.
My prefix is strange when you cut off its tail,
My infix a prefix, just think of Orwell.
My suffix reversed shall affirm and agree,
that when whole, truly epic this journey shall be.
What am I?
Could you be
ODYSSEY?
My prefix is strange when you cut off its tail,
Ody $\to$ Od $\to$ Odd.
[Confirmed by OP]: I was supposed to remove the last letter in the word odd, namely d, to make od (which is spelt rather strange, or odd). It was the "tail" because it was at the end of the word.
(And I noticed that since Odysseus is a Greek Mythology story, if we correspond the letter d with the fourth letter in the Greek alphabet, we get delta $\delta$ which looks like a tail!)
My infix a prefix, just think of Orwell.
This refers to the English author George Orwell who is best known for writing the book, 1984, of dystopian fiction (where the clock strikes thirteen!).
My suffix reversed shall affirm and agree,
sey $\to$ yes.
that when whole, truly epic this journey shall be.
/ Riley's Journey
That's what an Odyssey is about (The Odyssey by Homer; Odysseus Greek Mythology; 2001: A Space Odyssey by Stanley Kubrick).