Oh man those were good books. TV show sucked though. Should have just made it a cartoon so they could actually show the aliens. There was probably at least a squad of Hork Bajir in every book. Why on earth you would make a show when you could barely do half of the things the books did is beyond me.
And the books were great. Started off very kiddy but eventually the kiddiness was just a mask for thins like child soldiers, slavery, Post Traumatic Stress Disorder and all sorts of things. There were arguments with a Yeerk that revolved around whether it was evil for them to enslave other species when it was in their biology to do so. They couldn't really live any other way. Also, Andalites turned out to be kinda villains themselves. The only good ones were Ax and Elfangor. I always though that the entire war could have been resolved if Andrea from the Hork-Bajir Chronicles had died in the blast that killed her family. Without her around the Yeerks could have taken a few Arn and then had the technology to build their own hosts. No more slavery required.