Welcome to our forum.
I would basically second what CielDuMatin said: Try to be flexible about all three people being into each other equally. All people are unique, and each dyad relationship is unique. Any person in your triad may very well be into one person more than another, and forcing (or pushing, via expectations) the issue may cause some drama and heartaches.
As far as reading about experiences similar to the one you're contemplating, you might try a tag search for "triad."
You could even try a tag search for "unicorn." There will no doubt be a lot of threads to sort through.
No need to rush into anything, take your time and invest some research into the subject.