Starting with ADOM II 0.3.0 the game will provide access to a special "hints" mode that tries to help you to learn all commands. Below you can see a screenshot of that new mode from one of my debug sessions.
I actually am quite happy with its simplicity. It sports little details (you e.g. can click on the highlighted areas to activate the command explained there). It adapts with every move and tries to guess reasonable commands to choose from.
Hints mode right now is only available when you start a game as a beginner (e.g. from the new beginner screen) but starting with ADOM II 0.3.1 you will be able to turn it on/off in every game.
This is somewhat enhanced by the addition of the contextual action command suggested by Darren Grey in this blog post. SPACE will try to choose the most reasonable cause of default action for the PC when pressed - again starting with the next release of ADOM II.
Both new features probably can be enhanced quite a bit over time but for now they should be a starting point in order to help to reduce the learning curve for the game a little bit.
The hints mode BTW also will be the starting point for tutorial like explanations. I'm still hoping to add that to 0.3.0, too, but I'd prefer to get the next version out before the end of the ADOM crowd funding campaign, so we'll have to see about that.