An Expensive Place to Die, by Len Deighton. A spy novel and 1960s psychosexual drama that is interesting as a historical document but completely uninteresting as a thriller, a mystery, or a novel. Deighton was a popular author in the 1960s and 1970s... so I'll be charitable and assume that this is not his best work. (An aside: Deighton was no dummy. His analysis of the nuclear state of affairs in the 1960s, used as a backdrop for this novel, was spot-on.)
Consider Phlebas, by Iain M. Banks. This is the first of the "Culture" novels and the ideas presented are vast, tangled, and breathtaking. This is not a perfect novel and has two especially rough passages that can seem unconnected, in pace and delivery, from the rest of the whole (the first of these is the protagonist's escape from the island of religious fanatics and the second is the panic-striken escape of the CAT from the General Systems Vehicle (a term that won't make sense until you read the novel, sad to say). The subtext of the novel is the question of personal loyalties.
The Algebraist, by Iain M. Banks. This is a science fiction novel in the grandest sense of the word. Completely breathtaking. This is not a novel of the "Culture". The nominal antagonist, a powerful empire-ruler who is self-named Luseferous, turns out not to be the 'true' antagonist of the novel, and as such his role is abortive--he drives some of the plot elements, but not enough to be essential. He strikes me as completely nonessential--in a more refined version of the novel (a remix, if you will), he would probably not even exist.