I don't have any specific recommendations (other than seconding the outstanding advice to read The Hitchhiker's Guide [and you might as well follow that up with the Dirk Gently series] by Douglas Adams) but thought you might find this site useful: FictFact. I just found the site a short while ago but it seems to do a good job of taking a series name (e.g., 'Twilight' or 'The Earth's Children') and showing all the books in that series. And here's a link to their 100 most popular YA series. 100 Most Popular Young Adult Series. Hope this helps.