A GM's job is hard. There's loads of planning and prep work required. Sure, we've all run a game session "by the seat of our pants" before (I admit to running a couple sessions barely remembering where our party was last time, let alone knowing where I wanted the thing to go. Be fair, though, it'd been months since our last game). So having supplemental material around to be able to draw from can be critical. Thankfully, anthologies like Golden Age Adventures are around to help us out.
Though most supplemental books will be a couple pages, maybe several dozen, this one's a bit bigger. Heck, it's probably bigger than the rulebook for whatever game you might want to use it with, clocking in at 364 pages. The book has 16 adventure modules, 4 Death Worlds, 7 Hexcrawls, 48 Missions, and new and expanded rules (though the book, itself, is system-agnostic, so you can use it with whatever game you want).
The game takes its inspiration from well-known science fiction stories from the 30s-50s. You get the text of these stories along with the adventures based on them, so you can get some context and a bit of background information into what you're getting yourself into.
You can check out the supplement's list of authors as well as pick up a copy for yourself from the Daytrippers website.