I've been to Tibet five times now, and each time I have carried my now well worn copy of this phrasebook with me. Without it, I'd be at a real loss. It is has proven wonderful for communicating with locals - not only in Lhasa, but also in far more remote parts of the country. It is safe to say that using this phrasebook has enhanced my experiences in Tibet many times over.
If I did have one criticism of it, it would be that while it does have a brief English to Tibetan Dictionary in back, it would greatly benefit from a Tibetan to English Dictionary as well. So many times Tibetans have picked up the phrasebook from me and searched in vain for a word that they are trying to find.
But that criticism is minor. If you're traveling in Tibet on your own, this phrasebooks is a must. Depending on how long you're going to be in the country, you may want to consider the LP Mandarin Phrasebook as well.....