Flatland by Edwin Abbott Abbott, is a classic. Published in 1884, it is a satire on life during the Victorian era. Secondary students can read the story a few chapters at a time. It can be purchased, but it is available on line.
In the 18 page packet you will find an introductory list of reading questions for students as they get into the book as well as a list of questions broken into sections that go into a little more detail. There is also a list of projects that students can complete once they have read the book. Several resources with hyperlinks are included as well.