Captivating and annoying
The premise for the show and the core theory behind it is very intriguing. And because there is a lot of data missing due to the crimes being done so long ago, it's fun to use the imagination and fill gaps. But the lack of actual hard evidence and the over willingness of our two leads to put stock into things without real proof is just flat out frustrating and annoying. Episode after episode they hear something without actual merit that somewhat forwards the original theory and that new bit of non proven evidence now becomes functioning evidence in their investigation. What a load of bull.
By the end of the show ***SPOILERS*** they have essentially convinced themselves that Jack the Ripper was an American doctor that killed people with a surgical knife and that very likely Holmes and the Ripper were the same person. Nobody really knows anything about Jack the Ripper. No one knows his nationality, or weapon(s) used, or if the Ripper was one or multiple people, or if Jack the Ripper was even male or female. Them walking around with confidence claiming that the Ripper used a surgical knife for sure was one of several annoying allegations they consistently made.
Also bothering is their use of "well it hasn't been disproven" which became their tool for their theory somehow being sound. That's not how logic and formal investigation works. They should have not made any declarations unless actual evidence was found.
Having said all that... the concept that H.H. Holmes could have been Jack the Ripper was intriguing enough to watch the show. The background information on Holmes and the Ripper by several experts and historians was excellent. I just wish the leads of the show didn't try to shoehorn that information into their theory.