While Mumbo Jumbo is a very difficult book to read, especially at the start, it is far from impossible. Though on the surface it appears to be in some points a mix of gibberish, typos, and random things, such as pictures and quotations, thrown in without much explanation, once you look a bit deeper, it's possible to somewhat ignore or gloss over some of the extra, strange, information to get to the core story. In general, it's not nearly as different from normal novels as Reed would seem to want you to believe, as it uses many of the same conventions as most novels do, albeit in slightly different forms.
The start of the book has by far the most prominent examples of this unusual style of writing, from the oddly-placed first section to the short chapters that jump around to the huge amount of new, unfamiliar terms. It almost seems as if Reed is attempting to provide some sort of shock value in the beginning, to show just how strange this book is going to be by going all-out with the first few chapters. This section was the hardest for me to understand by a very long way, but, as the book goes on, it becomes much easier. Though the reader's progression and ability to pick up the meaning of some of the terms through context are part of what makes the book easier to read later, it's also in large part because Reed writes the rest of the book in a much more normal way. There is a decrease in the number of sudden images, strange phrasings, and the like, and it begins to read more normally. While the actual ideas of the book continue to be extremely out-there and strange, such as the search for the Talking Android using skin-altering cream, the claim that Warren G. Harding is actually black, and countless others, the language used to convey them is actually not all that unusual by the end. In the section discussing the history of Osiris and Set especially, perhaps in part due to the change in narrator from Reed to LaBas, it was easy to "forget" that I was reading this supposedly strange Mumbo Jumbo, as it seemed pretty much like any normal book in places.
In addition to the writing style becoming less unusual as the novel goes along, it also becomes more clear that the structure of Mumbo Jumbo as a whole is fairly conventional. The extremely disjointed, short opening chapters with limited connections between them in terms of characters give way to those that are generally longer, and sketch out a continuous, central plot with recurring characters that serves as the backbone of the novel and has a somewhat "normal" arc up until its resolution at the end, using some quite popular storytelling conventions. In addition, though the book in points has places where it seems to want to appear free from structure, such as Chapter 1 being located outside the usual boundaries of the story and there being two separate Chapter 52's without explanation, these are more an exception than a rule, and the novel as a whole is fairly bound by traditional chapter structure.