This sounds like a "Duh", but what is the purpose of having the students do the summer reading? How can you assess that purpose?
Consider creating a list and include at least one common, required book
----- to set the tone for the year using a book to introduce the opening theme for the Fall.
----- to give students a common piece of literature to talk about at the beginning of the school year .
----- to assess/measure what students know and are able to do before you settle on the lessons for the opening few weeks of school.
You could give one of those quickie objective quizzes to validate that knowing the who, what, when, where, whys and hows of a story. The scores can be recorded, but not weighted heavily enough to be viewed a major blow from which students would find it difficult to balance with later grades.
Then, move on to something collaborative, artistic and verbal that can help you learn what your students know about literature, literary terms, working together, writing and speaking. One such assignment is a COLLAGE. See other book report options .
The collage project is a four day assignment that students complete in class as you observe them working. By the end of the week, you will have a sense of who works well with whom. Listening to them discuss ways they're going to complete the collage, you gain insight into who's comfortable with the language of literature and what you need to review before moving on the new vocabulary. The project includes an oral component, so you get to see who's comfortable speaking and who will need a little encouragement. It ends with an in-class reflective writing that can serve as a baseline sample for their writing folders/portfolios.
And, the artwork provides decoration for the classroom that shows right away that students are important and also can remain on display for the first Parent's Night of Classes held early in the Fall term. Parents and guardians like to see their student works on show. Grades for the art project also are recorded, but again, not weighted heavily.
Here's a link to a simple "Did You Read?" Cartoon assignment.
Your local library probably has a summer reading program to supplement the incentives you may want to offer. See Collaborate Llibrary Summer Program.
Take a look at ways to tailor Ted Talks resources to help meet Common Core Standards for English Language Arts.
Plan a Pecha Kucha presentation to introduce your themes for the new school year.
Enjoy your summer doing the kinds of things thay renew your spirit as you spend time with family and friends.