CDISplayEx Free Comic Book Reader. This free CBR Reader has ads, but they are few and far between. It comes with the free trial of the paid version. CDISplayEx is an easy, light, fast CBR Reader, and in my opinion is the best CBR reader on the market. It can read all CBR format comics (.cbz file, .cbp file, .cbr file), and all Manga formats (with the free trial).
It can read comic books instantly, even without a CBR drive. I use this feature for many of my comics I'm currently reading, like the ones from Image Comics, Bongo, and Boom! comics. I've also been using it for some of my classic comic reprints, including the one that started it all for me, Batman: The Long Halloween. It can also read all of the popular graphic novel formats (.Epub, .azw, .txt, .html, etc.). Everything is designed to allow you to have the best possible comic reading experience - it load comics right away, they're easy to read and comfortable to read.
All of the features are available to you for a free trial. If after that trial you don't find yourself wanting to purchase the full version, you can simply uninstall the trial version and you will be ready to go. I like CDISplayEX, but I still use my old, trusty CBR reader, even though it's older. The free version was just okay to me, so it wasn't something I really got excited about, but the free version should work for you if you're looking for something similar.