When their small boat is washed ashore not far from their home, a brother and sister are unconcerned until they realize they have been transported back in time.
I've been researching San Diego ghost stories, and I thought this little book might be pertinent. Of course, it's a children's book -- and a short one at that. Every other page is an illustration, so it's even shorter than you expect. The story is about a couple of kids in 1977 (the year the book was purchased) who mysteriously end up in 1877. There's the expected confusion about that -- and then all four kids meet a ghost girl from even earlier. As a story for kids, it's okay, but there are better books out there.