Considering how slow it is to make books, especially the higher types, it's a bit annoying the way I have to waste books in order to create a specialist explorer.
Consider, for example. I have a Savage Scout and I want to optimise him for finding adventures. It starts off well enough: I add 3 manuscripts and that speeds up adventure searches. But then I have to add 2 more, because to apply any to the next level needs 5 in the levels below. But, in the first level, all the other options do nothing for adventure, so those 2 are wasted. That done, I can apply 3 tomes which give me more map fragments, all well and good. Now he has 5 manuscripts and 3 tomes, but in order to apply tomes to the next level up (where I can reduce adventure search costs), I need 10 books in the lower levels which means I have to apply 2 MORE manusricpts (I hope, not tried it) before I can do that.
I've not looked any further up the tree as yet, but I fully expect the same issue further up.
There are 2 reasons this sucks: firstly, it uses up books to no effect and secondly each explorer has a maximum number of books. I haven't yet worked out if you want to *really* specialise whether you can in fact get all the bonuses you want without running out of spaces.
There are 2 ways this could be addressed:
1) either change the requirements for books in levels below so that they go 3, 6, 9... rather than 5, 10, 15... (so that you can fully load one slot in each level and progress to the next level up)
2) change the arrangement of the various benefits so that books go to something useful.
I think I prefer 1 (and it's probably easier to code) - the same issues apply to geologists, for example if you want to make an iron specialist, you have to apply some books to something non-relevant along the way to access the upper levels of the tree.