Past computers did not come with quick start sheets or awkwardly worded manuals that barely scratched the surface of the product. They came with programming manuals, listings of memory maps, I/O registers, schematics and everything else the tinkering engineer might rely on.
The PageTable site contains a literature category, holding many gems. Some of historical interest, others of a more nostalgic nature (German). Now I just need to locate my old PDP manuals and contribute!