If you read one series by applegate, read this one.
Because of the three, this is most definitely the best. Remnants mocked the very idea of continuity (but was good despite that). Animorphs suffered at the hands of ghost writers after about book 22 when Scholastic wanted to keep a book a month pace and Applegate just couldn't do that. The quality just varied too greatly in the final stretch, when it should have been getting ever more awesome (nevertheless, it was very good). This doesn't have any series qualifiers like that; the only one is that it ends abruptly, leaving you wanting more.