This book was written by an American who hates Islam. I don't know much about his religion therefore I don't think it is appropriate for me to comment on his religion. Vice versa I suppose [with due respect].
However there are many American Muslim in America who can and should respond to most of his allegations and 'proof' because it is written in his language.
I've seen the 'strategi kristian' in you tube by former Indonesian nun, and it is shocking how they are making move to convert all Muslim in Indonesia. She said that Muslim must study their vision and mission and use this idea to fight back.
One of the issue she said was, Jesus was formally recognised as God by human beings only in 325 AD. She said how can human beings came into consensus and agree to select one of the human being as God. She said human is human. Human can never be God. This is a word of former nun. She continue, a table is a table, it can never be its creater ie the carpenter.
Jesus's birthdate is never mention in the bible or recorded but in the same year [ 325 AD] they adopted 25 December ie the same date of Sun God. This move was made to encourage citizen of that country to become Christian. I don't say this, the former nun did. Please search further if you want detail info.
As for the Christmas tree, this tree is not found in the birthplace of Jesus. It is called evergreen. Please search for yourself how this tree come into being during Christmas.
My deduction; only former Christian can answer allegations made by Christians against Muslim because you know them better. Better still if you are close members of the church.
By the way, more intelligent people are converting to Islam. If this 'deen' is so bad, why this is happening?