I can’t decide which system book to get next

TLDR; being that I’m a 5e GM, a solo player and I’m also designing a 2d6 Mad Max genre game, which physical copy should I get: Shadowsun (currently on KS and comes with GM and player books for $80 + shipping), Into the Odd for $40ish, or Knave 2e for $35?

I have been branching out into a variety of OSR/NSR systems and most of my collection is digital. I am really getting sick of digital media. I never really loved it to begin with, but that was what was most convenient for playing online. I have about a dozen physical copies of 5e 2014 books, but I am not putting any more money into 5e or 5.5 if I can help it, just because I’ve spent enough and feel confident as a DM to cobble cool stuff together for my 5.5e group and we haven’t even finished playing half of the adventures I own, whether digital or physical.

I have the Shadowdark physical and just love this book and the system. But I’m also curious about Into the Odd with its beautiful art and would like to get Knave 2e in print (also because of the artwork, but those tables!). I’ve also been very curious about Dark Sun since I got into D&D 6 years ago, and when WotC announced a 5.5 version I got excited. Then I learned about the mature content and I’m not really that interested in nudity or gratuitous violence since I run games for teens. Then I learned about ShadowSun for Shadowdark and thought that sounded slicker than what is, except it’s expensive.

I actually hate spending $40-$50 on books, which is another reason I just go digital, even though it’s not my preferred format. So pitch which book you think I should get next or offer an alternative to the three I listed. Thanks everyone!