"On the eve of his death, a person buries a rare book in a place known only to him. Assuming there was nothing built there would it ever be possible to remember his past life and reclaim the book? Also, can past karma be wiped clean, and have this incarnation be the last?"

Both Good questions.

So, can we remember our past lives? The book in this link and the case studies shown on the website would suggest that yes, it is possible.

I would say however that personally I have found that the more detailed the memory, the more traumatic the events associated with it. So for example, your chances of remembering where you buried the book are improved if you have some kind of landmark nearby and are in the process of dying under difficult circumstances, say being bitten to death by a pack of mad yaks...

Regarding the idea of 'moving on' instead of returning to Earth for another life, by having your Karma wiped clean, I have some thoughts on this, although none of this can I back up with empirical evidence of course.

Karma first of all. In the 1991 movie "Dead Again", Robin Williams described Karma as the Cosmic Credit Plan; buy now, pay later. Many faiths include this concept. The Christian "As ye sow, so shall ye reap", for example, is spiritually equivalent to the Wiccan rule of three. But does Karma exist? There is an Amish proverb which says:

"We did not inherit the land from our fathers. We are borrowing it from our children."

If we are our own children and grandchildren because of re-incarnation, then that means if we screw up the planet now, we get to see the results in the next life. So, if reincarnation exists then so does Karma.

But do we have a soul? The Taoists and Sufists believe that the soul is a latent potential in all humans, something that can be awoken. The bible is always banging on about 'His eyes were opened' , as if in that moment the person finally got it. It, one can assume, is the soul. One of the key components of Hermetic belief is the concept that at death those negative energies that exist in a human being are de-energized and recycled. Only the purified, cleansed 'gold' of the spirit, empty of lead, can ascend past the abyss of Da'ath. So, if you spend your life tied in to the material world, always hunting for a faster buck, identifying yourself based on the position of power you hold or how much money you have, what will all that mean when you die? Nicht. Zip. Squat. Nada. Nothing. That may be a good example of how to live (and die) soul-less. If your life revolves around the interplay of social circles ("OhmyGodIcan'tBelieveYouSleptWithHimIThinkHe'sCute DoyouThinkThisMakeUpGoesWithMyHair IloveThatDressItsSoCuteItWouldBePerfect ForTheClubTonight") Then you may not be spending enough time awakening your soul. It is said all Dogs go to Heaven - sadly, I don't think the same can be said of Mall Rats.
But if you can look at yourself and strip away all the pieces that are dependent on this world to exist, and then still be left with something, then you may be waking. And when you can look at that something, and see how it is damaged, how it can be made better, and what things you can do to affect that change, then you are awake.

In the end, if the essence of you can exist without any external support - without money, cute clothes, social position or power, then that essence may well survive, when you pop your clogs. That is your soul, and it is that which can move beyond this life or return if need be for some additional 'sprucing up'.

Anyway, that's just where my head is at right now. Your mileage may vary...