This has a neat premise that has been done before, extremely poorly, but I'm willing to see if it does this premise properly, or to see if the protagonist buys a flint lock or a cap and ball revolver
I think this premise is extremely difficult to do well. A perfect guide (in the form of a book, a god or... a magic internet)
means that the MC basically knows everything they need. So, assuming there is no barrier to growth, they can train the most effectively, collect optimal gear and get through most challenges with advance knowledge of their solution.
This makes the MC's intelligence and resourcefulness irrelevant. Most of the time, even decisions become irrelevant as they are told the optimal path to anything.
The only bit of challenge left is for them to have the personal skill and courage to go through the recommended path, but it's not like any of these manga even try to make you doubt that the MC will survive. (However, some authors do scar their MC with seemingly permanent injuries. Severed arm, lost eye, that kind of thing. Pretty rare though.)
(Note: the worst offender of them all is the manga with the MC that has an "auto skill". He doesn't need to know anything, because he doesn't even need to
do anything. The skill does it all with guaranteed success. The pinacle of lack of agency.)
I'll still have a look, but my expectations are low.