Dengeki Pikachu is based off the Pokemon Anime, but with a handful of twists that in my opinion make it more enjoyable.

One of my favorite things about Dengeki Pikachu is that the author makes it more "realistic". By that I mean Ash has to pass a test to get his trainer's license, going to school is discussed, and the more "technical" aspects of being a trainer are further explained.
Also, the artwork is more realistic. Pidgeoto looks much more like a bird, and Butterfree looks a lot more like a real butterfly

The characters are developed more than they are in the anime. Its still Pokemon so you can't expect too much, but by Pokemon standards, its pretty good.

Gary and Ash have a lot more interaction in this manga as well. Gary has a sister which is a source of comic relief (on Ash's part)

Overall its pretty funny and interesting. Misty and Brock don't always travel with Ash either, letting Ash do a bit more developing on his own.