Why is Urrea's novel so complex and demanding?

Luis Alberto Urrea's novel The House of Broken Angels is so well written at times, w/ beautifully evoked scenes and encounters, sharp character delineation, a great sense of the history of a family over 4 generations,t racking the assimilation (or not) into life in the U.S. and the gradual evolution from being Mexican to Mexican-American to simply American, a really fine novel, but devilishly difficult to read at many points, particularly in the final section, Big Angel's 70th (and last) birthday celebration. I'm reading the novel for the 2nd time and am still completely lost and confused at various points as I try, hoping against hope, to keep some of the peripheral characters straight: who's married to whom?, who's divorced from whom?, who's a child, a grandchild, a great-grandchild?, who are these many cousins?, who's related by blood and whom by marriage?, and I could go on. I don't think it's just me, and I definitely don't think it's Urrea's mistake. He's intentionally written an exceptionally demanding novel that requires our full attention and at least one re-reading and possibly extensive note-taking during the process of reading. Is it worth it? Well, this novel is not as great in scope as, say, 100 Years of Solitude, nor as groundbreaking in style and intellectual depth as Ulysses nor part of a grander scheme of works, like Absalom, Absalom! - so, no, in a way the demand on the reader is too high a price. But in another way, I've come to think that Urrea is intentionally creating confusion so that we the readers will feel like a guest who has meandered into this lively celebration - knowing some people, not knowing most, figuring things out as we go along - an interactive, participatory novel, in its way.