Okay, slightly more seriously, summer reading lists tend to be good for this. A number of teachers will try and pick higher interest reading options, and a number of schools try and provide a variety of options to suit a variety of kids. Here are some options from a quick internet search:
(and Merriam-Webster came in as the last suggestion 
!)
But essentially, whatever interests a kid enough to read will end up helping. And that can also include graphic novels. This page discusses graphic novels and comics and how they can play into building stronger readers: Debunking Myths About Graphic Novels and Comics to Unlock Learning | KQED. One quote from it includes:
While comic books and graphic novels may contain fewer words per page than the average chapter book, the authors are required to choose their words more carefully. ā[They] reach for a higher-level vocabulary word that says in one word what the average person might take six or seven words to say,ā said Jones. A study by the University of Oregon found that comic books average 53.5 rare words per thousand, while childrenās books average 30.9, and adult books average 52.7.
Some graphic novels that Iād bet have much higher rates of rigorous vocab include those from Classical Comics which has versions with the original text, whether Shakespeare, Frankenstein, Jane Eyre, etc. Or thereās something like Sophieās World, a melding of fantasy and history of philosophy and has a graphic novel form separated into Vol. 1 and Vol. 2 (with the samples of Vol. 2 showing some of the more complex vocab that the Vol. 1 picts donāt show). Graphic novels from Neil Gaiman, or an adaptation of Slaughterhouse Five or the graphic novel classic The Watchmen.
Anyway, just wanted to offer some suggestions and resources that might help.