Our five-year-old loves the "Magic Treehouse" series!
http://en.wikipedia.org/wiki/Magic_Tree_House_series

We used to read one of the books in the evening, but the books didn't last that long that way! So now we read it over 3 nights, and then have him read us another book for a bit more instead. It's kinda exciting to look forward to how the story ends. Plus it's sad but sometimes I learn stuff from these chapter books.

Do you read chapter books in a single night, or over several nights?