Since somebody shared this nice comic about manuals in games in another community, I was thinking about them myself.
My most cherished game manual was the Diablo 2 one. The way they created a little story for each single ability was such an atmospheric wonder and probably started my fascination with lore instead of story. They were also probably the main reason why I took the necromancer and started to feel bored, when necromancer are automatically evil in a setting. Get creative!
My father had Falcon 4.0 and that was “just” a technical manual in itself. 5+ cm thick and full of schematics of the cockpit. I was in awe as a child about the complexity of that thing.
I think my favorite single moment, a personal anecdote, relating to video game manuals is from Where In The World Is Carmen Sandiego for Windows 95. Which came with a full copy of the 1995 World Almanac. I was about 8 or 9 at the time. One of the clues was “I heard he was leaving Lesotho by car.” I went, “Wait, is that the little nation in the middle of South Africa?” I looked it up in the book, it was, and I won that round of the game based on that clue.
I think my overall favorite video game manual has to be the one from A Link to the Past. A lot of manuals had maybe a prologue or backstory in the manual, A Link to the Past has like three, including the creation myth of the in-game religion. Go read ALttP’s manual and tell me it hasn’t been the design document of the entire series since.
One more: For some reason, Illusion of Gaia for the SNES includes a full walkthrough right in the manual. They just outright spoil the entire game in the manual. Not sure why they did that.