Hindu philosophy is about the soul; it's nature; it's relationship to God. It is the same today as it was a thousand years ago, for there is nothing in there that can change.
Hindu religion or Sanatana Dharma on the other hand is about people, guidelines for people, how they should live, what they should and should not do etc. and therefore cannot be the eternal truth.
The Bhagavad Gita is the crown jewel of Hindu philosophy. It is the best gift that God has given man (hmm .. I wonder if God's love for man is his best gift .. hmm i dunno .. i feel God's love for me is my rightful inheritance; I am ever grateful for it, for it is causeless and will never ever go away, but it's not a gift, it's the birthright so to speak, of every soul.) But anyway .. the bhagavad gita can never ever get outdated or needs to be headed with discrimination ..
The Manu Smriti etc on the other hand are so very different. They are like the Old Testement of the Bible. They talk about social conduct, rights and responsibilities of women etc. which sort of change from age to age ..
I found "In search of the supreme" by Gandhiji in my school library. It was interesting to find books by Gandhi and Nehru in a school in New York ! The book is interesting, totally sincere and honest. So many useful ideas.
Gandhi was a truly wonderful man...