1 point in advanced engineering increases the probability of book drops for four skills: electrician, traps, workstation, and repair tools. 1 point in locking picking increases the drop of forge ahead books up to level 15ish.
As to vehicles, I agree that the progression is too slow and that max books should probably be dropped from 100 to 75. I have ended up restarting before I've reached gyrocopters in each of my playthroughs. I've also had no luck with loot drops or trader inventory in this regard. This is probably my least favorite part of 1.0. I didn't play too much of A21 but in prior alphas I was always able to obtain all of the vehicles through a combination of looting and buying from traders before I got bored with that particular save.