I used to read a lot of kids books before Animorphs (Goosebumps mostly, and several other 'scary' titles), but none of them really stuck with me, and they were pretty forgettable on the most part. Animorphs is what really got me hooked onto reading though. At the time, I thought it was the most revolutionary thing ever written, mainly because I had never read a story so realistic and fantastic at the same time. It was very relatable, and you could easily loose yourself and believe that you were living in their world with a secret invasion carrying on around you.
Years later, I'm still finding myself thinking about the series and talking about it one way or another. Heck, I've been known to spend days just looking for specific items or facts or images for my website alone. So yeah, Animorphs has deeply affected my life, and it still does to this day.