Guides vary in length based on subject and author style. You're objective should be to create the minimum amount of content to accomplish the objective of the Guide and really "wow" the reader.

Then once it's launched and you've been able to collect feedback on that minimum amount of content, you can make it much more robust.

However, some of the most popular Guides are comparable to the size and length of this Guide. On average that's 6-10 sections and about 25-40 Pages using a mix of written content, images, external resources and videos or audio clips.