I'd have to say it depends on your study techniques and speed you can learn complex topics. The LR bible is massive, and it took me forEVER to plow through it, and I'm still going to have to go through it again. I'm almost done with the LG bible, and comparatively, I'm tearing through it. MUCH simpler and faster, for me.
I'd still recommend buying it, as it's valuable, and I'd think you will need to learn techniques from somewhere, if at least for the types of problems that repeatedly give you trouble. I wouldn't plan on breezing through it, though. It's not a quick read.