Most of the heroes that Burroughs has created are cast into exotic locales: Africa, Mars, Venus, and so on. Barney Custer, the hero of The Mad King, gets to go to Eastern Europe. He also has to try to be a swashbuckling hero in twentieth century Europe, with World War I as the backdrop for at least part of his action. The result is a tale that, while set in a more or less realistic setting, seems far less believable than John Carter's adventures on Barsoom.

The story is set in the fictitious country of Lutha, a tiny European kingdom apparently located in the mountains bordering Austria and Serbia. Barney Custer is traveling there, visiting the native land his mother left to come to the United States before he was born. Barney gets caught up in a series of adventures stemming mostly from the fact that he bears an uncanny resemblance to the supposedly mad king of the country who has been kept confined for years by his uncle, the regent. In the first half of the book, Barney saves the king, restores him to the throne in the face of a nefarious conspiracy, and earns the wrath of the king he saved. In the second half, set during World War I, Barney saves Lutha from an Austrian invasion, tries (and fails) to save the king, becomes king, and wins the girl.

Barney is a decent swashbuckling hero, and his adventures are certainly loaded with derring do, but the book just doesn't seem to ever rise above adequate. Setting the story during World War I, when swashbuckling was consumed by the machinery of modern warfare is probably the biggest problem with the book. Custer is also supposed to be a superior swordsman, but he only uses that skill once or twice early in the book, after that, all of the battles feature revolvers or carbines, as if someone read the early chapters and pointed out how silly sword wielding heroes in the modern era seemed.

As I said before, the big weakness of the book is trying to set a swashbuckling hero in the middle of a modern war. The book was written in 1914, before the carnage of warfare in the industrial era had become apparent to those in the United States, so the book seems to have an odd unreality to its battles, with saber armed cavalry sweeping across artillery positions, and generals heading to the front to rally the troops, and so on. Everything in the book is all very romantic, and heroic, and ultimately, tragically innocent. Unfortunately, real history proved that people who try to swash-buckle their way across the battlefield get filled full of shrapnel and lead. Custer's story ultimately fails because he is set in the wrong era. There's nothing wrong with Custer himself, or his individual adventures, but the setting is all wrong, and the overall story never rises above average as a result. ( )