Yes. I understand this point. But if you seriously learn a software then you always have to read manuals. I remember learning Lightwave or ZBrush. I could never achieve this without tutorials and manuals. A 3d engine even needs much more examples and tutorials.

The best engine documentation that I ever got my eyes on is the documentation of TGB (Torque Game Builder - the 2d engine of Torque). You have so well written tutorials, several small games as examples to teach you the techniques and of course a list of all functions, properties and parameters at the end plus a well working search engine.

The best documentation of a 3d-modelling application is the one from ZBrush. It also supports many examples to guide you into the insides of the software.

I think this is very important. A list of short descriptions is nice and is a good compendium but to teach an engine it needs knowledge about the insides the coherences, interdependencies and more. Little examples are the best way to do so.

I still work with Delphi 5 and often checked the later editions of Delphi. But the documentation got worse with every edition. The reason for the Delphi-breakthrough simply was the geat documentation. Almost every command came with an example in the online help. And the help always is just one key away. If I place the cursor above a command and press F1 then I get the fitting help page and an example.

The examples are often at their own pages since they fit to more than one command / function / structure. So they have links from various pages. That even helps to minimize the amount of examples.