It depends on how much background you have in each of the papers. For instance, having done A level bio and chem, and AS physics, if I could go back in time to the start of HSFY, the only textbook I would've gotten was the one for HEAL. I found all of the papers except for HEAL192 straightforward enough that the slides were sufficient. HEAL192 I needed the textbook to know what the hell was going on lol.
And if you're at a hall too then it's easy to borrow your friends' textbooks. They won't mind

You see them lying around unused anyway

I only rarely the textbooks apart from the HEAL to look up some minor things, which I could've easily done by borrowing someone else's book.
Luckily in my year they didn't test stuff from the HUBS book. I didn't bother to do the HUBS readings. Are you 100% sure the material was exclusive to the readings and was not on the lecture slides and not mentioned by the lecturer? It seems slightly unfair to test on something in the textbook.