Excel books/resources or formulas

I expected to see a separate forum or something on this subject because surely it has come up thousands of times but at the risk of annoying, I will ask. I'd like the gurus' opinions on the best books or perhaps online courses for Excel formulas (I'll attempt macros and VBA later). I have received help with formulas but sadly would have to admit that I can't translate what the formula is doing. I realize trial and error is likely the best way to learn but often in the work environment, there usually isn't time for that. Thanks all!