I picked all three of them up and played thru all 3 of them one after another, i enjoyed them mostly tho i did have some minor gripes for all three games:
-story is pretty lackluster and doesn't really go anywhere and there are a few too many pop culture reference jokes for my taste.
-higher difficulties are not particularly hard they're just damage sponges that take forever to kill even with glass cannon builds that rely on kiting.

Having said that i did enjoy the game and katarina has her pretty funny moments, i'd recommend going fairly tourist mode low to medium difficulty and just enjoying the playthrough for what it is.