I should think that a required reading list should include a great mix of classic works (novels, plays and short stories); a variety of genres; and a touch of modern works (future classics). I would also be sure that this list supplemented material that I was teaching in class during the particular school term, and that it might also be useful for future English classes.

Like most districts, my district has a required reading list for each grade level, but the list has numerous novels from which the teacher can choose.  There are specific books on that list earmarked for the gifted and talented program, pre-AP, and on-level students.  For example, the on-level students read The Outsiders when the GT students are finishing up The Taming of the Shrew.  When considering choosing a book, I would always opt for picking a book with a higher than grade level lexile ranking, just because my district is very AP oriented and I want to prepare my students for high school English.

One of the great freedoms, however, is literature circles.  I use literature circles in my classroom to introduce those higher (or lower) level books for my readers of varying abilities--and since these are smaller groups, I can bring in more modern or edgy texts that build reader interest. 

I think that a good reading list has a balance of classics and new texts, books of different genres, and topics that are relevant.  A book like To Kill a Mockingbird might be a classic, but it deserves the title.  Its themes are still relevant.  Kids are still drawn in by the characters and amazed by the beautiful language.  Yet a more modern book like The Book Thief also belongs in the curriculum.  Last year I had a student raving about the book say, “It’s just different!  It doesn’t seem like a school book.”  Kids need to be introduced to all of the doors that reading opens, and that means a well-balanced diet.

I would like to say that I pick my AP Language lists based on the "best" books, but we only have 180 days, so I try to get the best "bang for my buck."  I pick works that may be on their AP exam next year, but that will also help them on the AP exam this year. And though they may not agree, I also try to pick books that will pique my students' interests enough to get them to read them. Most of the texts we use are the traditional American Literature books, The Scarlet Letter and The Great Gatsby, but I also look for works that are provide a richness in which students can analyze the author's rhetorical decisions. We will read Huck Finn since the themes developed in it can help them next year, but can also be used to analyze satire, regionalism, and the journey.  Because of this, I look beyond the Lexile score and look at what we're doing with the text. 

Grade- and reading level appropriateness are important, too. You can go to lexile.com and type in any book to find out what lexile number the book has. This can help teachers to advise students on what to read in their reading range while also providing proof/data to support your decisions.

But a Required Reading List is for a class or grade level, rather than individual students. Lexile ranking can be used to tailor a reading list to the overall reading level(s) of a class, but there are other things to consider too. For example, a novel that has fairly sophisticated themes or a tricky plot line or an ironic narrator may be inappropriately targeted to a younger readership, based on lexile ranking alone. Conversely, a more difficult work may get overlooked even though the story is compelling enough to inspire less skilled readers to get through it.

Should a Required Reading List take lexile ranking into account to ensure that a range of difficulty is provided? To eliminate too difficult or too easy books?

Grade- and reading level appropriateness are important, too. You can go to lexile.com and type in any book to find out what lexile number the book has. This can help teachers to advise students on what to read in their reading range while also providing proof/data to support your decisions.

One factor that makes a great "Required Reading List" is making sure that there is a diversity of works across different genres and styles of writing. In addition, a great list would include excellent literary tomes from other countries. Furthermore,  a great list would include the works of the major masters, as well as quality literary writings from contemporary and new writers. There is some excellent writing even within genre fiction. Moreover, a great list would include non-fiction, essays, short stories, poetry, and even quality scriptwriting (plays, short scripts, screenplays). The reading list does not have to be limited to literary novels. In fact, a truly diverse, eclectic, and vibrant required reading list would look for these different types of writing and wholeheartedly embrace the best of them.