Question: It seems pretty normal to see screenshots of MS Word, steps for "this is how you generate a template". I don't think Microsoft would object.

But I'm not sure about reprinting images from in-game scenes for specific games, like Diablo II. Do you need to obtain permission to include a screenshot of a game in your book?

Answer: 
There is a legal consideration concerning using part of one copyright work in another. The rules around it involve the quantity of material copied and the purpose for which it used.

However in your case there may be an over-riding consideration. If *Blizzard Entertainment* took exception to your use of material from *Diablo II*, would it harm the market for your book?

If there could be a negative impact from not seeking approval, then ask, whether or not you are strictly required to by law.
The copyright information included with the game itself should tell you the answer to this. They will set out the parameters of what you can and can't do.

My hunch would be that a specific screenshot of a game in action, created by yourself, would be considered 'an original creative work' and would therefore not be restricted by the game publishers copyright rules.

However, you would really need to consult a lawyer specialising in copyright to know what you can and cannot do legally.