You could give Terry Pratchett's Discworld books a go. Light, funny easily reqdable. Very clever and well observed parallel takes on this world.
Second the recommendation for Rebus novels by Ian Rankin.
If you fancy a bit of History in your detective stories, C J Sansom writes a series of novels about a Henry VIII era lawyer Matthew Shardlake. Very readable and well researched.
I like Jon Ronson's books too.
I've found some absolute gems in the free offers and 99p books by new or unknown authors. For that money you can take a punt and if you don't like it, so what.