I am not going to be commercializing this TTRPG, so that really shouldn't be a major concern. All of the fonts I used (Impact, Spectral, and Georgia) extend rights to universal use on non-commercial projects. As much as I would love to collect some money I can spend to pay copy-editors, artists, graphic designers, advertisers, and the like, I just don't think I could have the time to manage a business.I use office libre to write chapters and then cut and paste it into affinity publisher for double column. One thing that gets over looked is that fonts are not free, such as arial, something to look out for.
The page size for the Guidebook is still standard paper at 8.5 x 11.5, it's more that the font size (DoS uses 12, D&D uses 9), font type (DoS Spectral Medium, D&D uses Bookmania Regular, the latter of which is smaller), margins (DoS has 1", D&D has .625"), Indent Extent (DoS has 10 spaces, D&D uses 5), and a few other small details. Obviously, the font size is the big game-changer here.No worries. I'm thinking the reason I'm seeing it as a wall of text even with indentation is possibly because the traditional size of an rpg book is 8.5 x 11.5 inches and the impression I had was that is the size.
Novels on the other hand are smaller and I don't have the same problem. And books such as Shadowrun 5E have a 2 column layout so again I don't have that problem.
Other rpgs published as smaller books (6 x 9, 5.5 x 8.5) also don't give me this impression even with a single column layout.
Here is what the Introduction would look like if represented in D&D style: .
Here is the D&D 5e preface for comparison:
Though now that I look at the document, I do recognize that the paragraphs for DoS may be longer than they need to be. I wonder if the reason why you are having trouble reading it is actually due to the paragraph length and not the line spacing. Let me try an experiment: is this easier to read?