So far as people have bested the solution I could come up with, I suppose I'll post the one that was in the book as well (again paraphrased to account for some changes I made):
Suppose the ropes are called rope A and rope B. Climb up rope A and cut about 99 feet off of rope B, leaving just enough to tie a loop with the remaining top portion. Tie this loop. Slide back down rope A, and tie one end of the cut portion of rope B to the bottom of this rope. Now, taking the other end, climb back up to the top, and feed that end through the loop until it's close to touching the ground. Then, swing over to the double rope you've just made, and slide rope A off of its hook, letting that end fall to the ground as well. Climb down this double rope which is hanging about 6 inches off the ground, and then pull on one of the ends to get it all down, which is about 199 feet.
Of course, if you assume that you can feed the rope through the hook like a pulley, as other solutions have done, it also becomes possible to get all 200 feet, by eliminating the "forming a loop" step:
Climb up rope A and take rope B off of its hook. Slide down and tie rope B to rope A. Taking the other end, climb back up the the hook and slide the end in your hand through the hook until it touches the ground. Then, swing over to the double rope, and slide rope A off its hook, letting that end fall to the ground as well. Climb down your double rope, and pull on one of the ends to slide the other end off the hook, getting all 200 feet of the rope down.
I've since found the old puzzle book that this puzzle came from (Giant Book of Mensa Mind Challenges, 1998 ed., section 1, puzzle 196). The solution in there is presented as follows:
First, tie the lower ends. Then climb up the first rope and cut the second one, close to the ceiling, leaving an end long enough to form a loop. (You can instead cut it off entirely if you slide the rope through the hook.) Hanging from the loop, cut the first rope at the hook. Be careful not to drop it. Then slide the rope through the loop until it's even. Climb down the double rope, and once on the floor, pull one end to get it all.
This solution involves grabbing hold of the loop or hook and hanging from it while working with the other rope, which seems a bit dangerous. I prefer my strategy (which is the same except doesn't involve hanging 99.5 feet off the ground) which involves one more up/down trip but never puts you in a situation in which you might conceivably end up stuck hanging near the ceiling if you're not careful.