Update: This offer has ended.
Another Prime Day deal from Amazon will take $5 off any physical book worth more than $15. This deal doesn't work with third-party sellers, even when fulfilled by Amazon, so make sure it says the book is shipped and sold by Amazon. Use code PRIMEBOOKS17 during checkout to get the discount.
Here's a couple books that fit the bill:
A Gravity's Rainbow Companion at $24.67 - for those of you like me who don't understand Thomas Pynchon
Humans of New York at $16.86 - for you people watchers
1000 Record Covers at $17.99 - if you're really into records
To Pixar and Beyond at $15.65 - if you enjoy reading about both Pixar and Steve Jobs
Also, if you're more into Kindle ebooks and not physical books, there's a deal on Kindle books as well. Buy any Kindle book and get 40% off your next book purchase.