For some reason, many reviewers here seem to compare Jerusalem with Infinite Jest. I don't see anything similar between the two, besides the length and pages-long walls of text.

"This will be very hard for you", says one character in the book, and reading this book is hard indeed, but there is no payout of any kind. It just goes and goes and goes.

I have to confess that Jerusalem is one of these extremely rarely books that I did not finish. Somewhere near the end of Book Two I've decided to check reviews on goodreads, and some of the most unflattering ones were describing what I was feeling, and so I realised there is no point in further miserable waste of time. I'm no literary critic, and English is not my first language, as you have probably guessed, but in some cases you don't have to be an expert to tell flies' crap from an ointment, and I believe Jerusalem is particularly fitting case. It is as if it was written by a student who just wanted to make a pretentious brick of a work.

Plot is extremely self-contradictory. Some examples from Book Two (which is the only one that seems to at least pretend to have a conventional plot) (yes, that's the one that describes chocking on a cough pill):

Narrator: painstakingly describes for 10 pages how there is no time in afterlife, and how our spacetime is seen just as 4-dimensional brick from there. Time: flows.
Narrator: painstakingly describes for 10 pages how, because there is no time, people can't even utter words such as "is", "was" or "will be"; even when they try to say these, they actually say "wiz". People during the next five pages: only say "wiz" instead of "is", "was" or "will be". People on the next 300 pages after that: routinely use "is", "was" or "will be" without giving a second thought, with occasional appearances of "wiz". Probably Moore has originally written these chapters in more conventional style, had to replace all the verbs by hand because his text processor does not support autoreplacement, got tired of that after first five pages.
Narrator and protagonists: describe for 50 pages how they can effortlessly jump from one time to another, with a minute-level precision. Protagonists: "oh, we don't have time for that, we should hurry up, or we'll be late for some meeting in another era".
Narrator: so this three-year old kid looks like ten-year old and has a mind of adult person in afterlife. Protagonists: interact with that person like it is adult. Also narrator: repeatedly uses "toddler" to refer to that person for the next 300 pages. Aren't toddlers supposed to, well, toddle?
Narrator: so there are these heavenly creatures who are also angels and unimaginably just and fair and who basically built that place and who deeply care about people and everything. Two most important angels: after having a minor disagreement, without attempting to solve it by civilized means, start a fist fight that reverbates throughout the entire world and threatens to destroy a significant part of their project.
Narrator: so this protagonist girl is so shy and tight-lipped that it is rarely that you hear a single word from her, let alone two words. Girl: constantly interrupts everybody with her walls of text.

There is no a single relatable hero. Although on paper they're supposed to have some distinguishing traits, they all act the same. You have dozens of POVs, and they only differ by external events.
For most of the book two, protagonists just aimlessly go from one place or time to another, with a fake sense of great urgency and need. Protagonist: "OK, now we need to go to X, hurry up everyone!" Why X? Why is it important? Why do they need to go there? Protagonist does not explain and does not know; nobody instructed them to go to X. Once they arrive to X, they just look around, and soon afterwards "OK, there is no time to look around, move on, we need to get to Y!"

And writing is just abysmal. It is what happens when lazy student wants to dilute their short essay to comply with the minimum length requirements. You get adjective and adverb abuse going on a horrendously scale, and a whole load of repetitions put on top of that.
A typical sentence from Book Two: "Phyllis shook her head in a briefly-enduring smear of features, much like when you drew a face in ballpoint pen on a balloon then stretched the rubber out". It was preceded by about a hundred of other similar descriptions on how everything looks in that place. We already know how it looks when somebody shakes their head, protagonists know that, narrator knows that, it does not add anything new and does not build up an atmosphere, there is no need in describing this yet again, unless you want to make your book several hundreds pages longer.
And Moore, knowing that repetitiveness is a sin, tries to state these repetitions in a different way. While half of time he's using the same adjective, in another half he's trying to replace it with some synonyms. He probably had A Complete English Thesaurus With Even The Most Obscure Words at his hands, and of course with such an enormous book he runs of common synonyms shortly, and so in addition to all of the above the book is peppered with Big Words, that serve no purpose but to further obstruct the reader.

TL;dr: There are no ideas in this book, nor is it an enjoyable reading. You'll have to wade through barely readable low-quality writing and not get anything in return.