I don't have a lot to write for this Thing. I wrote about my library roots and route a couple of years ago, and while I've moved on a bit in job terms since then, my history in libraries hasn't!
I don't think my path into special collections work has been particularly unusual. It's certainly been marked by a fair dose of good luck at various times. My advice to other people would be to grab chances to gain experience whenever they come along. You never know when they might come in useful in the future!