My son has been reading The Magic Treehouse books, but has been bothered by the occasional violence and fighting and good vs. evil themes. He's a sensitive soul, and we are a family with pacifist values, so we're looking for alternatives. Can anyone recommend chapter books at a similar reading level that are adventurous but not about using violence against the bad guys?
It might seem too young, but depending on your son's age it might work. The original, not disney-fied AA Miline books are actually quite good.
Try the wizard of oz series. The bad guys try to fight but the good guys are pretty good at coming up with nonviolent solutions.
I don't know if they would be too girlish, but my DD loved the Big Apple Barn series and I was really impressed with the thoughtfulness of the (animal) characters. They're about horses, and have no violence whatsoever.
We are in the middle of The Penderwicks and no violence yet.
I love the little house books but some have quite a bit of violence. Farmer boy includes a story of students beating a teacher to death and the next teacher uses a whip to teach those same boys a lesson.
There were a lot of great books listed in this thread, but I'm not sure about the violence/non-violence aspect.
We've been reading Beverly Clearly with my nearly 5 year old (Ramona and Ralph S. Mouse so far), and she loves them. We've been passing them onto a friend with a 5 yo son and he's similarly enamored despite the female character. I would agree that the Little House books might not be ideal at this point if he's sensitive. The early books might not have person-on-person violence, but Laura Ingalls Wilder didn't sugar coat the reality of life on the prairie. We're saving them for when DD is a little older and has recovered from the trauma of meat harvesting and prairie fires.
Ruth Chew wrote a lot of books about kids discovering magical things. The ones with "witch" in the title are a bit scarier than the others, but none have violence or terribly evil characters.
Miss Osborne-the-Mop by Wilson Gage is a wonderful story of two cousins who don’t want to spend the summer together in the rural mountains but bond after they accidentally turn a dust-mop into a sort of person and then lose the magical power with which they created her and have to figure out how to hide her from the adults and tolerate her annoying personality. SPOILER: In the end, the mop-person has a fatal accident, and it's just after her death that they figure out how to turn her back into a mop--so a character dies, but she is really a mop, but if your son is very sensitive about death you might want to avoid this.
Someone recommended Charlotte's Web, and I have to point out that that one not only includes the death of a main character but also is primarily about trying to prevent another main character from being slaughtered and eaten!!! I found it pretty upsetting when I was 7.
Encyclopedia Brown books by Donald J. Sobol present mysteries for the reader to try to solve--and then look up the solution at the end of the book. Some characters are a bit intimidating, but there's no violence that I can recall.
Eleanor Estes wrote several books about the Moffat family, kids in the 1910s doing various fun projects and having small-town adventures.
I just want to point out that the OP asked for books at about the same reading level as the Magic Tree House books, but I don't think any of the suggestions offered in this thread so far are actually at that level - they're all more difficult books that might work as read-alouds but probably not for the OP's son to read to himself. I'm not sure I can come up with any good suggestions myself, though. The Boxcar Children is a bit higher reading level that the earlier Magic Tree House books, but might work. I don't recall any violence or bad guys (in the first Boxcar Children book, anyway), but the kids have adventures. After the first book, it turns into more of a mystery series and I wouldn't be surprised if there are some bad guys. Probably little if any violence, but I can't say for sure.
Ruth Chew's books are similar in reading level to Magic Tree House. I discovered them in second grade, when they were offered on my book order form distributed at school, so they're about second grade level.