I got a copy of Figure Drawing for all it's Worth by Andrew Loomis for Christmas, which is awesome. So, naturally I'll be working through that for the next little while.
I've spent some time over the past few years in learning to draw, so some of the material in the book is stuff I've covered before. And sometimes in learning a skill, you'll find that you're revisiting stuff you'd already learned.
The important thing in that case is to keep paying attention. Don't take anything for granted. There's the temptation to skim over "blah blah blah, I already know this stuff" but if you focus, and bring your more developed sensibility to the "beginner" material, you never know what new insights you can find.
There's no lesson that you can't still make new discoveries from, if you approach it with an open mind.