The Racional Vol. 3 is a boot, and is one that I have been after myself (I have Vol.2). The Racional Volumes were originally on Maia's own label, Seroma. He recorded it in 1975 for the Racional Culture, the religion/cult he was part of and fell for deeply, so much so that he quit drugs/alcohol, painted all his instruments white, wore white clothes and would regularly play in fields to attract aliens. Anyway, later that year he realised that the religion was a sham after discovering that the leader had stashed away thousands of pounds which were meant as donations. Maia was so embarrassed that he had fallen for the scam that he ordered all the Racional volumes (2 were released but a third exists which was not released officially - which looks to be the one you have!) to be destroyed. Those few that were remaining have become prized possessions.
Anyway, these bootlegs are really the only chance of having them on wax (unless you get insanely lucky and find an original) but they really are not bad sounding at all.