Once again the American First Day Cover Society is making its publication First Days available to non-club members online via a PDF.
It is a specialist publication, so if you're new to the world of first day covers, expect to be surprised by this byway of stamp collecting. And it is the current issue being offered, so you'll get a good crash course in what first day cover collecting is like now.
As the quickest way to learn to swim is to dive into the water, here is your opportunity to get in the swim with first day covers, aka FDCs. If you're still not sure, allow me remind you that it's free.