I guess the first thing to be considered, for many perhaps the only thing to be considered with regard to Adam Levin's massive novel The Instructions is length. Although not quite matching James Joyce who needed 760 odd pages to chronicle the events of one day in Dublin, since his 1,000 plus tome covers four days in Chicago and environs, Levin has produced one hell of a long book. Of course, you could argue that since Joyce deals with two characters, not counting Molly, and Levin deals with only one, it is necessary to divide the pages in Ulysses by two and those of The Instructions by four in order to get a more accurate comparison. Then, of course, why not count Molly? In which case, the numbers are closer. Then again it may well be necessary, for accuracy's sake, to think about words on the page. After all Ulysses in the Modern Library edition hasn't quite the page size of the Canongate edition of The Instructions. It doesn't come close in bulk either: simply holding Levin's book to turn the pages is something of a chore. Suffice it to say this is one long book.
(To digress for a moment: if the kind of Talmudic analysis merely hinted at in this opening paragraph is not your cup of tea, if you think of it as nit-picking, you probably aren't going to care much for The Instructions. A good many of the 1,000 plus pages are taken up with precisely this kind of analysis of what characters say, what they write, what they do. Hardly anything — whether a wink, a nod, or a casual remark — goes unanalyzed. End of digression.)
Length doesn't particularly bother me. When I finish one book, I start another. It really makes no difference how long a book is. Still, if you are going to spend the time on a book of this length, might you not be better off with War and Peace or Don Quixote? Back many years ago, a professor of mine once suggested a standard by which to test a work of literature. Ask yourself, he said, does the value you get from it justify the work you have to put into it. He wasn't necessarily talking about length only, he was talking about all the effort necessary to read a work and understand it. While this is a fine standard to measure a work's value, it is necessary to read the book and do all the work before making your judgment. If that judgment is that it wasn't worth the effort, you've in effect wasted all that time that might have been put to better use. On the other hand, as a critic, if I have done all that work and discovered that it was worth the effort for me, how can I know that all readers will end up with similar results?