I have read it several times at ~12, ~25, and again in my late 40s.
It has the illusion of depth and will certainly strike a chord with some, but its not altogether that great a book in the opinion of many, but exactly the kind of book that others will swear by.
That's because most focus on what I was supposed to be indoctrinated by: Jonathan's journey and ascension.
Nobody expected I would fall in love with Fletcher, read the book as a long prologue to Fletcher's part, and make his words the hymn to my liberation: "No limits, Jonathan?".
It has the illusion of depth and will certainly strike a chord with some, but its not altogether that great a book in the opinion of many, but exactly the kind of book that others will swear by.