When a player chooses a new talent, he does not see 1) the talents he already has, and 2) the talents he can take in the future (but not now).

I know that there is a [?] key that shows the appropriate section of the manual, where you can read about all the talents.
Nevertheless, I remember that I didn't know about talents like iron/steel skin and others for quite a long time.
I suppose that I'm not alone in this matter... some people don't read the manual attentively.

I propose to show all the talents in the talent choice screen.
Divide them into several groups:
1. talents you already have
2. talents you can take right now
3. talents you can't take now, but can possibly take in the future (even better if the prerequisites are marked: fulfilled/not)
4. talents you can't take in the current playthrough (because of not being dwarf, or missed Alert talent, etc)

Also it would be nice to change the order of the talents.
So that the talents which depend on each other are shown close to each other.
The alphabetical order is not better than a random one...