PACKBACK's backpack just got a little fuller with a new $1.5 million funding round, led by Hyde Park Angels with Wintrust Ventures, Mark Cuban and Howard Tullman (CEO of 1871) also participating. Founded in 2013, the Chicago, IL-based startup and Shark Tank contestant offers a library of digital textbooks that students can rent by semester or by day (for under $5). The new funds will help Packback grow its 10-person team and further refine a new offering, "Packback Answers," an online study group where students and professors who are using the same textbook can help each other. More details from ChicagoInno.