$100 Gift Card, Please Help!

Hello, fine people!

My best friend's step-dad recently gave me a $100 Chapters/Indigo gift card to thank me for some genealogical research I did for him. I'm a huge book nerd, but I am ashamed to say, I've been stuck in an author rut for awhile. My last year or so in books has been: autobiography/biography of someone I like or am fascinated by, a Stephen King novel, a book of poetry, another Stephen King novel. I need some suggestions on how to use this gift card in a way that will get me out of my rut.

I enjoy:

-Stephen King (obviously), more specifically his dark fantasy and crime novels
-Guy Gavriel Kay (but don't suggest a book by him, as I have read them all)
-Patrick Rothfuss
-Margaret Atwood
-Mark Twain
-Ernest Hemingway
-Poetry of all kinds, but particularly that which is subversive, counter-culture, political, etc. Favourites include Lawrence Ferlinghetti, Maya Angelou, Sylvia Plath, Dorothy Parker, Leonard Cohen, Langston Hughes, Rudy Fransisco, and Neil Hilborn.
-Books about language, such as Reading the OED and The Rude History of English
-Non-fiction about crime, history, religion, cults, media, art, etc.

Help me spend this $100!