Eragon is pretty good. I used to like Artemis when I was younger. Harry Potter is a bit overrated in my opinion. I'm not sure if Sherlock Holmes counts as a series as they are somewhat independant of eachother. I really want to say Lord of the Rings, but Tolkien intended it to be a single novel. hmmm... quite a perplexing conundrum...
I like Louis L'Amour's westerns. I don't have the collection my mom had. It's funny but like her, I didn't really care for western novels until I hit my forties. Now that I'm becoming a history geek I appreciate writers like L'Amour who have lived what they write.
do warhammer books count as a series? no wait that's more of just what kind of world its set in right? because i've read a couple of warhammer 40k books
i like the Warriors series but a lot of people say its for girls, i don't know why. other favorites are the Seventh Tower series by Garth Nix and the Percy Jackson series by Rick Riordan.