I really enjoyed this one -- there were parts where I felt like it could have been tightened up a bit, but the story, the characters, and the overall plot were quite engaging.
An earlier review mentions Robert Donat playing the lead role, but for some reason I kept seeing Cary Grant running around through the moors. Not heavy reading, but a good story, with fun characters - a step above "pulp" fiction.
A very fast paced, forward looking, jargon-rich look at a post-singularity civilization -- great characters, and an intricate plot that could be expanded into an entire series.
One of the things I've always enjoyed about Sherlock Holmes stories is that while they're far-fetched they're not impossible, and that makes them more enjoyable. They're also really well suited to reading aloud, with excellent dialog.