Masonic memorabilia is a hot collectible today, so your Harry Truman autograph is worth more than it would be on the average book or Bible. How valuable, I do not know. You should search the net for Masonic memorabilia sites and ask your question there.
I can give you general Truman autograph values for material signed when he was not president:
Signature: $150
Signed Document: $350
Signed Photo: $300
My father left me a Masonic Bible that was signed by President Truman on January the 5th 1967.
