Okay, the way I think this works is that I have to read whichever book the first person to comment picks. I haven't read any of these before, although I've read other books in the series for a couple of them and have watched an anime adaptation of another one.
Baccano!, Vol. 1: The Rolling Bootlegs - Ryohgo Narita - An English translation of a Japanese novel. I've never read it before, but I've seen the anime based on it and enjoyed it. It's set in the U.S. (New York, according to the back of the book) during the Prohibition era. The anime includes people who have been made immortal by a special wine, plus loads of violence.
Only the Ring Finger Knows: The Left Hand Dreams of Him - Satoru Kannagi,Hotaru Odagiri - Another English translation of a Japanese novel. This one is m/m romance. I read and reviewed the first book in the series late last year. I though it was overall terrible, but entertaining.
Star Surgeon - James White - Sci-fi, part of the Sector General series. It's doctors and medical mysteries in space.
Resenting the Hero - Moira J. Moore - I think this one might be the longest one of the bunch. It's fantasy with a magical system that involves bonded pairs. There's humor and I think a little romance. Danielle's Reading Adventures liked it.