in that book the author puts forward evidence to imply that gandhi thought he was above black south africans. and going from the quotes in gandhis writings, it doesnt make him look too good. the tone suggests that he thinks himself above the black prisoners he was stuck with. but to be fair, the person he was in south africa isnt the same person he was decades later. i dont know for definite if he changed his views on black people but he did become more wise and open minded/enlightened in his old age (as did say, malcom x) and theres some quotes here offering some counter evidence that the guy writing the book conveniently overlooked:

“ England has got successful competitors in America, Japan, France, Germany. It has competitors in the handful of mills in India, and as there has been an awakening in India, even so there will be an awakening in South Africa with its vastly richer resources -- natural , mineral and human. The mighty English look quite pigmies before the mighty races of Africa. They are noble savages after all, you will say. They are certainly noble, but no savages and in the course of a few years the Western nations may cease to find in Africa a dumping ground for their wares.”
Gandhi, speaking at Oxford, October 24, 1931 (CWMG , Volume 48, p.225).

“You, on the other hand, are the sons of the soil who are being robbed of your inheritance. You are bound to resist that. Yours is a far bigger issue.” Gandhi to Rev S.S. Tema , member of the African Congress, January 1, 1939 (CWMG, Volume 68, pp 272-273.)

A deputation from South Africa led by Sorabji Rustomji came to India in 1946 (CWMG, Vol 83, pp 352-354). It was protesting against racial legislation in South Africa. A member of the delegation asked Gandhi: “You have said we should associate with Zulus and Bantus. Does it not mean joining them in a common anti-white front? “ Gandhi replied: “Yes, I have said that we should associate with the Zulus, Bantus, etc….It will be good if you can fire them with the spirit of non-violence”. (CWMG, Vol 83, p 353). Gandhi remarked of the deputationists’ cause on May 27, 1946 : “The cause is the cause of the honour of India and through her of all the exploited coloured races of the earth, whether they be brown, yellow or black. It is worth all the suffering of which they are capable”. (CWMG, Vol 84, p. 215).

Gandhi remained in contact also with leading American Black personalities like W E B Dubois. He wrote in Young India on October 14, 1926 about the “injustice that is being daily perpetrated against the Negro in the United States of America in the name of and for the sake of maintaining white superiority.”

theres some interesting comments about it here (its where i got the above quotes from)-
http://www.stinkzone.com/cgi-bin/archives/000056.html
you can make up your own mind