Don't judge on this figure, regularly see good quality houses on blocks that have 70%+ land ratio (Site value/Buy price)The land vs purchase price is 64%. Is it too low?
Definitely not too low, it's quite a high figure when talking about a house in very good condition, all depends though on the specifics. Can also get plenty that are 80%+, again it's not enough to judge just on the number by itself.
Check for the usual things, zoning of land and age of house, easements, flood and overland flow, boundary issues and so on.
They can be painful processes, you have a party on the other end of the contract who has as their main concern the idea of preventing litigation and covering their risk, no concern at all about getting the best price or anything you might be interested in, good luck!