Best Case Books/Study Guides for Undergrad Case Interviews?

Perhaps I'm a bit of a hardo, but going through the process and coming out of the other side, I would say that MBA casebooks (even if they're harder than what you would necessarily "need" to understand), are probably the best resource to pull from when you're trying to go through your preparations. Part of this is to do with the fact that, as far as I know, I don't really think that there are any good plentiful resources available at a specifically "undergraduate" casing level. The vast majority of casing resources you're going to find are going to fall under a dumbbell distribution of either being very beginner or MBA level. The other part is more of my outlook, but I think it's far better to be overprepared than underprepared when it comes to case interviews, especially if you're going to bat for more competitive positions and processes at MBB and some T2s. 

If you're really just starting out, obviously Case in Point is considered the holy bible but I would skim that and instead really opt for Case Interview Secrets by Victor Cheng instead. I think it offers a much better perspective and more structured lessons on the 'theater' and way a case interview is really supposed to flow. 

When it comes to case books though, I think Stern 2019 is a pretty fantastic case book, Haas ones too. Wharton also has pretty great casebooks as well in the more recent ones, though the ones online are a bit rife with typos which can be a bit disappointing sometimes. The LBS2013 casebook is also a uniquely difficult but incredibly detailed casebook that can give you a lot to learn.