I finished reading Rurouni Kenshin a few years back but it wasn't until a few weeks ago that I finally got around to reading a gift from a buddy of mine: Rurouni Kenshin Profiles.
RK Profiles is a 411 book on the characters in the RK manga series. Spanning the first two story arcs of RK, the book gives info about each character, their techniques and fighting styles. One of the things I've always liked about RK was that despite it being a fictional story, it was based around events that actually shaped Japan before, during and after the Meji era. This book also tells you about what types of food, clothing and other natural resources that that coming to Japan and when they showed up. So on top of getting facts about the cast and crew of RK, you can also learn a lot of other stuff.
Even if you've already read RK, you should still check out RK Profiles. There's also a timeline detailing the events and births of the key characters in RK and some colored Shonen Jump covers of RK that you won't see in the regular 28 volumes of the series. Sure, if you go browsing the net you can find them, but it sure is nice to see them on actual paper.
I got my copy for free, but I'd still pay the $14.99 if my friend hadn't gotten this for me as a gift. If you're into RK, pick this book up.