Definitely if it's not your job and it's just a hobby. Just like how a hobbyist coder can get by without reading any books or learning about design patterns, etc.
But if it is your job to use photoshop on a daily basis it's worth going deep into that tome.
It wasn't my intention to speak ill of good books on photoshop. I was just trying to think of an example. I'm aware that there are probably great books on Photoshop, and that probably most are.
But if it is your job to use photoshop on a daily basis it's worth going deep into that tome.