Pocket Monsters is a gag manga authored by Kosaku Anakubo that follows the adventures of the trainer Isamu "Red" Akai & his ill-mannered Clefairy. It's technically split up into five parts: The original Pocket Monsters(covering the RBY and GSC era), Pocket Monsters Ruby-Sapphire, Pocket Monsters DP, Pocket Monsters HGSS, and Pocket Monsters BW.
If the original Pocket Monsters & its sequels are treated as one continuous manga, it's the longest running Pokemon manga to date & the second-longest-running manga in Corocoro magazine. Pocket Monsters is the most popular manga in Japan, even beating out the likes of Pokemon Special. It even got a cameo in the anime! Despite this, it has never seen a proper western release - Chuang Yi has translated a few volumes, but that's all. One possible reason for this is a rather simple one: This manga has very crude humor, to the point where Red and his Clefairy appeared nude in the second chapter of the manga.
Bulbapedia has summaries for several chapters of this series(original series, Ruby-Sapphire, DP). In addition to this, Dogasu of Dogasu's Backpack has been summarizing the BW saga as it gets released - you can read his summaries here. He also has a summary of Vol. 1 of the original series that's more detailed than Bulbapedia's summaries.