Good gaming material is effectively systemless. While I don't play 5e, I can easily convert 5e adventures to S&W on the fly (although I strongly suspect going in the other direction would be much more difficult).
The Tomes of Lost Magic for 5e Humble Bundle has quite a few highlights. If you ARE a 5e player, you can buy in for a physical copy of Book of Lost Spells Hardcover and a boatload of PDFs for 38 bucks. If you AREN'T a 5e player, 18 bucks gives you everything in PDF, along with 30% off coupons for Frog God Games and Nord Games, as well as a coupon for World Anvil. Heck, if you don't want to convert from 5e, buy-in for a buck and you still get the coupons, and you can buy your Swords & Wizardry stuff from Frog God at 30% off.