Any novel written with half a brain and intended to engage a reader with a brain has ideas in it. If that is all it has it isn't a novel. It's an abstract treatise or piece of philosophical speculation. If it has no ideas it's probably a bonk buster.
That's true, but there's an important difference between a novel with ideas in it and a novel of ideas. Neither Joyce's Ulysses or Sartre's La Nausée could possibly be described as "an abstract treatise or piece of philosophical speculation" (nor, for that matter, a "bonk buster"). In each case the reader is drawn into the story and wants to read on because the story compels them, but what drives the story? What makes it unfold as it does? The author makes choices based on exploring their philosophical argument. The ideas are made gripping by the story and the suspense of story turns on the excitement generated by the next turn of the argument, rather than by, for example, the physical jeopardy of a thriller.
I thought carefully about these choices in writing The Human Script (please take a look at bit.ly/humanscript, if you're interested). I was anxious to let the ideas unravel in a captivating way, but in the process, I did not want to lose the readers' emotional investment in the principal character. There have been many kind responses to the book, particularly in praise of how thought-provoking it is, but the responses that really please me are those readers who say they were gripped or moved to tears. I could have written "an abstract treatise", but, by choosing to write a novel, I chose to embed the argument in a story that had to be every bit as important as the philosophical content.
Ulysses has linguistic interest but Sartre is just a dull Marxist who knew f all about human beings. His supposed explanation of why his mates ran away in 1940 and left Highland soldiers to die for France is completely without any intellectual or moral depth.
Intriguing thought. Situations are character driven where the action is central to the story and novel of ideas would feature explanatory text with a slow advancing plot. In the novel of ideas a character would be studious and reminiscent, allowing for the unfolding of cumbersome speculation to explore a theme or theory. In the novel of situations character dialogue is shorter and the action drives the story, leaving less narrative and a quicker rhythm.
I say a novel of ideas would need to express things that the reader has interest in and explore those ideas in new angles to make them provocative and fascinating.