Learn By Reading plus 1.0 loot/quest changes

Putting one point into Miner69 just makes good sense for the bit of boost it gives to block damage. But it will also help the harvest tool book appear a bit more often as well. Also check trader stocks at every inventory change because that book is a pretty common one they sell. Remember also that iron tools suck stamina a lot faster than stone tools so you don't want to graduate to iron tools until you've leveled up some and have plenty of coffee to support their use.

How many you've read of a magazine has no impact on how many you find of that book. What Skills you spend points in, however, does. If you Haven't put any points in Miner 69er, but Have put points in several other skills like a melee and ranged weapon, an armor skill, etc, Then you're not likely to find many of the tool magazines.