The "somebody else thinks like me" feeling is probably, mostly, a feature of psychological adolescence; by which I mean that transitional mental phase between childhood and adulthood: it is a feeling I associate with reading particular books, more than anything else.
(Although I did get it, albeit very rarely, when meeting a new person.)
A particularly memorable and clear example was Colin Wilson's The Outsider, which I encountered age 19; at a point when my mind had for several months been increasingly occupied by exactly the matters that were the focus of that book - especially the problem of the triviality, dullness, and alienation of mundane everyday life...
How there are experiences in which this alienation may apparently be overcome - but that these "moments" of fulfilment are always (it seems) brief and temporary, and incomplete.
Wilson's book was a thorough and multi-faceted explanation and analysis of the problem; such that I realized "it's not just me" who experienced modern life in this way.
My initial hope was, naturally enough, that Wilson's writings might be, or might point-to, The Answer; but of course that was not the case.
(I say "of course" because I now believe that there is no full and permanent "answer" to this problem in this mortal earthly life; because this life is a transitional and learning phase of an eternal soul, so this life is itself a kind of adolescence. Therefore a full answer that is the resolution of the problem is only possible by moving on to spiritual maturity, which lies beyond death.)
Nonetheless, it was a considerable encouragement to realize that I was one of many people who knew and grappled-with this problem - and who regarded it as a very significant problem. Since there was nobody in My Real Life who talked about such matters, or who seemed to take them with the seriousness that I did - The Outsider book - and those that followed along the same line (both by Wilson and recommended by him) - meant a great deal to me.
