When it comes to multivolume manga series, my preference is always to read through the entire series run in one sitting (or a number of continuous, back-to-back sittings). It gives you an expansive, broad-stroke perspective on the creation and the creator(s). For time's sake, however, I prefer to do that in English. Especially for series that are more than a couple of volumes. And thanks to more compressed release schedules than were common a decade or so ago, there are a number of fun series from which to choose. I read these two over the past week:
Basilisk by Yamada Futaro/Segawa Masaki - What can I say; I have a perverse fondness for eroguro...and this is definitely indebted to the genre, even if it's heavier on the "guro" than the "ero." The character profiles at the end of the final volume were priceless. Lots of fun and a lightning-fast read.
ES -Eternal Sabbath- by Soryo Fuyumi - I tried to read this one in Japanese back when it was still in serialization, but after pondering one too many text bubbles, I gave up. The language--biology! physiology!--was way too advanced. Besides, I figured it would end with Shuro and his clone locked in an embrace of mutual destruction, anyway...and I was right. Still, Soryo is a great mangaka, and she is just getting more ambitious with age. I can't wait crack open the Cesare thingie she's doing now for Morning.