Open stacks also meant that a lot of material got "lost" simply due to being misplaced (i.e. stacked somewhere it wasn't supposed to be). You could replicate the "proximity" simply by adding a topic classification to the library record, and making sure that users can search for "other books on this topic".
Google seems to look for the most relevant topics, then zone in on the one most likely yours, then fill the result set with topics mostly from the one it think you favor. At page three you'll find pages from all kinds of topics. I think this is an ok approach.
But what if instead you filled the result set with the top result from each topic, and then let the user select a topic to drill down, you could have a "more like this" link for each result item and topic. Wouldnt that more resemble what we like about the library? We want to find the right shelf, then browse a while.
