Heard: "World's Greatest Sleuth!" by Steve Hockensmith.

Heard: World's Greatest Sleuth! by Steve Hockensmith, 2011, Overdrive.com download.

Another excellent audio title with a great story by Hockensmith and narration by William Dufris.

Big Red and Old Red Amlingmeyer are working a sheep ranch in 1893 when they get a letter from Big Red's publisher telling them to come to the World's Columbian Exposition in Chicago. The letter includes a travel voucher and off they go.

The Exposition is hosting a World's Greatest Sleuth competition made up of famous detectives of the dime novels and magazines. (In these Holmes on the Range novels most of the famed detectives, like Sherlock Holmes, are real people.) Other detectives include a handsome NYC dude, a Hercule Poirot type, and a Sherlock look-a-like. Most important to the fluttering hearts and flustered tongues of the Amlingmeyer brothers is Diana Crowe (not Corvus).  Turns out Diana is the god-daughter of Colonel Crowe who still dislikes Big and Old after they helped wreck a train in On the Wrong Track.

The Amlingmeyers are slowly moving up in the world.  Big Red has been published and now, with the contest, Old Red has a chance at publicity that will get him a professional "detectin'" job.  Things happen.  Old Red is taciturn. Big Red is talkative.  Stuck up sticky beaks are starch shirted stooges. Diana is lovely.  Murder is deadly. The White City is a sight to behold.  Big Red and Old Red get in a hole (figuratively) and have to climb their way out. Old Red's skills are doubted, criticized, and put to the test.  Bad guys are caught.

Comments:
1. One of my favorite series. I checked Hockensmith's web page to see if any more books were planned. Hockensmith's comment from July, 2014 says, The boys will definitely be back one day! And "one day" is finally starting to look like it's coming closer. If all goes according to plan, I might have something to announce by the end of the year....
2.  When I worked at the U of I Main Stacks I ran across a set of folios on the White City that was full of sketches and designs.  I would see many, many neat items working there.
3. Yes, the main stacks did have a "vault". It was a caged off area in the stacks for items that were prone to theft.  Sex books like topics on auto-fellatio (marked missing) and sex manuals were there.  Other items like illustrated histories of military uniforms were also shelved there.
4. The main stacks were expanded after I graduated with an off-site storage location. I don't know if the items stored in The Vault of Sex and Theft were moved.