SpellObjectEnthusiast
Adventurer
They have a tier for backing only a single book for those who can't afford all of them - and each book comes with all the bonus goodies associated with that book.The Battlezoo Books look like they would add a lot of interesting options to SD and the price of $50 per book (US at least) is pretty reasonable, but releasing them all at once and bundled together seems to be too much for most. I think a staggered release would have been better, but maybe logistically this made the most sense for them?
Will probably pick up the PDFs to see if physical is worth investing in. Appreciate the art is in tune with Core the books.