One of the most obvious ways to divide your massive novel into sections is chapters. There are pros and cons to their length, which is really up to you. Personally, I prefer shorter chapters since sometimes I don’t have a lot of time to read and I don’t like to stop in the middle. But this is just me, though it seems that everyone is pretty busy these days, so I don’t think I’m that unique.
Another way to divide your story is by including more than one scene in a chapter, perhaps because you change point of view characters. In this case, it’s best to mark your section breaks with a few asterisks rather than simply rely on an extra space. This can work in a print book, especially if the first paragraph of the new section is also not indented, another visual clue to the reader that the scene has shifted. However, this might not be noticeable on an electronic reading device. I’ve encountered this before and it turned out it was quite confusing because the POV had changed.
This is another simple trick to let your reader know what’s going on so they don’t get lost.