I think the question you ask is really important. There are several cases.
For my little story, I currently write in French some article on Minetest. I test some mod and I spend most of my time trying to understand the different characteristics of these.
For example :
Ethereal NG, a really fantastic mod, add new bioms, modify the map generation, add new trees...but no detailed explanations are given in the forum post or on the github repository. A book would be a really good idea (explanations on the forum post and github too for sure). I had really big difficulties to understand how Ethereal NG and
More Trees! works together, knowing that for example they both add willow tree and trying to know how it works : do they both add the same tree ? If only one is choosen to be added, which one ? etc.
When a mod adds only decoration stuffs, a mod like
Craft Guide is sufficient, we have the recipes and the possibility to scroll among the new item, Craft Guide really helped me. Other mods modifying the player's inventory don't always allow to scroll among the item but only seeking by the name, which is not pratical if there is not so much documentation for players on the forum/github.
I play on Mynetest server, there is a kind of craft guide which fit to this issue, XDecor mod which is installed gives no explanation on items neither on the
forum post, nor on
the github. I have no idea except browsing the code to understand fully what fantastic things this mod adds.
Another case, when a mod add complex new items, book with text isn't a good idea, craft guide is practical to find the recipes and try but external documentation is really needed as it is done for
Mesecons.
Mesecons is a good example to solve the issue : nobody install it without having gathered some information on it which are easily available. But a mod modifying map generation, a book with text would be a good idea (and more documentation too).
To summarize :
- Craft Guide integrated by default would be a good idea, maybe optional activation
- Book with text to present mods which modify the map generation
- Better documentation to players for each mod more generally, I personally would like to help with pleasure but I'm not a developer yet, able to understand how it works only by reading the code (even if I try and succeed sometime).