This is classic high space opera on an epic scale. There are two parallel stories. One is a story of an ancient AI that has gone berserk and that is taking over and corrupting much of the Galaxy. That story is a lot like something that Dan Simmons or Iain M. Banks might right, but not quite as good. It has some early riffing on the internet (the book was written in 1992) and sees the internet (here Galaxy wide) as a place that people post stupid rumours and nonsense with the occasional bit of truth. This story is only OK. It has some clever things, in particular a galaxy where the laws of physics work differently and science and mentality can be more advanced as people move out from the centre. That's cleverly done, but this part of the story while good would not be enough to make the book a classic.
The second part of the story which runs alongside the first concerns a war between two factions of an alien species called the Tines on a planet with medieval technology with two human children involved. The Tines are hands down one of the best alien races ever conceived. They are dog like creatures that become sentient in packs of four to six. So the individuals are the packs which share a group mind and not the individual dogs. That is really well done, very well thought out and the aliens are very vividly and realistically made. They are easily one of the best alien species ever in any medium.
The book is written competently but the prose lacks artistry. I don't know that the book has much to say and it is really just an extended adventure story, but my those Tines are awesome. There are also another alien species called the Riders which are well done, but would not count as one of the great aliens of all time.
You should read this book if you like clever space opera or for the tines. Outside of interests in space opera or very inventive aliens, there is not much else here of significant interest. Its basically one of the best pieces of science fiction that has nothing to say.