Thank you for your response Naren. I see what you mean by calling overrideSelector twice in the test since we are skipping the first value, which makes sense. I took what you posted and changed it to:

// Arrange
store.overrideSelector(selectBooks, [{ test: 1 }] as any);
store.refreshState();

// Act
component.getSomething();

const mockResult: any = [];
store.overrideSelector(selectBooks, mockResult);
store.refreshState();
flush();

After that it worked/passed great. Thanks again!