I homeschool and one of my favorite kids reading resources is the curriculum company www.sonlight.com
They are really big on using great reading books as part of every curriculum. You can actually go on their website and look at the lists of books they use for different reading levels. We have never been disappointed with any book we have read that they use. I have bought several curriculum packages from them, but I also sometimes just look at the book lists if I am looking for a book for one of my kids that is based on a certain topic, or on a particular reading level. And then I order it online thru the public library or try to find it used. Many of the books are Newberry award winners so they are not that hard to find used.
I noticed it says you are from Mission Viejo. I know this is not super close, but it's not ridiculously far away either. There are two used book stores owned by the same guy, they are called Piccolo. One is at the Howard Hughes Center, just north of LAX. The other is at the Pike in downtown Long Beach (next to the convention center). They are well worth your drive. They have a million used books it seems, and every book is $1, that's it. I have taken my children's book lists in there, and found lots of the books for $1, instead of paying a premium to buy them new.
Another good book resource is a book called Honey for a child's heart by Gladys Hunt. I know it seems strange to read a book about good books, but the book lists in there are invaluable, and it also talks about why we should be reading these good books to our kids, because they are honey for a child's heart :)
Lastly, my kids loved the Bobbsey Twins books. They are very family friendly mystery books from the 1950's I believe. My mom read them, I read them, and I'm so thankful I saved them for my kids to read. I don't think you can buy them new, but I have looked on the Los Angeles public library system, and you can order the ones they have on interlibrary loan. I can't say enough good things about the Bobbsey Twin books, all kids love them! Make sure you are getting the original hardcover series and not the newer paperback series that they tried making in the 1980's as easy readers. Totally not the same.