No book is ever as good as that one you read as a teenager. You probably remember it - that one which you picked up and just couldn't stop reading, which then formed the basis of your emotional core for years to come. You read it once, and then probably several times afterwards, each time reinforcing its imprint upon your very being.
How would one go about finding another such book?
One approach might be to look at that first important book, to see if it has any particular qualities that distinguishes it from other books. It is easier to find things when you know what to look for, after all.
Thing is. Upon returning to the book of one's youth, there is a non-zero risk that one might discover it to be less impressive than it is in memory. The years between then and now have included many things - books, experiences, life events, deaths - which put things in perspective, and changes one's outlook on things. There is a risk that, upon returning, the book turns out to be the most bland, generic, run-o-the-mill piece of prose there ever was.
This does not diminish its value or the validity of your experiences. It does, however, draw attention to the importance of context. When a book is read is as important as what is in it: in the hands of a young person in search of meaning, any book can become an ontological and emotional foundation.
If you happen to have kids of your own, the thought of leading them towards a similar book might have occurred to you. This, again, actualizes the question of how to find such a book, and how to introduce it.
Simply telling them to read something might do the trick. Sometimes, life happens in straightforward ways.
More often than not, though, it will be something unexpected. They will pick up a book, read it, and - wham - that's the one. There is no telling which one it is, but that's the one it is now, until they become old enough to remember that book they read as a teenager.
The key, then, is to give them ample opportunity to stumble upon a good book. Keep your home well-stocked with good books, and allow access to them at all times. Play the odds. Make it more likely that the book they stumble upon is something by, say, Gloria Anzaldúa rather than by - I shudder to think - Ayn Rand.
Life is full of surprises, strange turn of events and curious edge cases. Sometimes, it is no accident that we stumble upon them. -