When it first came out I remember a review which said it was 'difficult to read because of the disjointed conversations which didn't clarify who was speaking' and occasionally when the conversations went on for pages I understood what they meant. It also said the book was Romeo and Juliet through time and space, and I can sort of see why the reviewer said that without necessarily agreeing whole heartedly. It's the sort of reductive comment I tend to deplore; I remember an English lecturer once describing Gaskell's North and South to me as Pride and Prejudice in Victorian costume which missed so much of the point that I couldn't; be bothered to discuss it.
Red Shift was weird, but it was also wonderful, and honestly I don't think you can appreciate it on a first reading so I shall reread it another time now that I have some understanding of the structure and themes behind it. For what we would now class as a YA book, it was a challenging read, technically and emotionally, but worth it.