So plenty have mentioned this novel as some sort of Scottish Ulysses - which appears to be rather bizarre to me. There is an entirely delicious flirtation with the Dante-esque here (and, to a lesser extent, Joyce's Portrait of the Artist as a Young Man, particularly in the presentation of Hell in Book 1). Gray is incredibly attentive to the details of The Divine Comedy, employing sly references drawn from throughout the trilogy. I'll briefly indulge myself in a few:
Lanark's short flight referencing the last line of the Inferno (rebeholding the stars); The giant and prostitute; the three beasts of the mount embodied by three women in the opening; the delightful attention to the tensions between light and dark, which is particularly elucidated (and often overlooked) in Paradiso; Rima (Dante's rhyme scheme being, of course, Terza Rima); Gray's own appearance that appears to suggest both the God of Paradiso (I think Gray has seized upon Dante's description of God as a volume - the book!?), and more subtly, the devil himself.

I'm sure I'm being tiring already but Thoughts are happening.

I think what is important about this novel, among other things, is the manner in which Gray observes and complicates the classic in a new way. It is one thing to mimic Joyce, and transplant the epic into the modern, but I think Lanark achieves something new, escaping the Modernist structure and diving into a postmodernism so gleefully postmodernist it becomes almost onanistic.

I think I'll contain myself there

So I was thinking 4 stars for a long time but I knew when I encountered the twists and turns of the final book that I'll keep thinking about Lanark - so 5. Terrible rating system anyway.