Is my history book biased?

I don't know if I would say "biased", because the editors of the book most probably just wanted to present the most popular position, without caring much about correctness. You are, however, always free to buy yet another history book and use it for reference. If your teacher is really cool, he/she would let you cite data from more than one source. Although I am happy with my history book, I also have another. I use both simultaneously to be sure that I always get the right idea even when historical sources are unclear or there are contradicting POVs.