I am having trouble understanding why a woman is not allowed to speak in the church, but she can write a book and it appears to be OK by a lot of Baptist Preachers.

 I understand that writing on doctrinal issues is a form of teaching.  However, the restriction in scripture is specifically against the public teaching of men (1 Timothy 2:11-12 [11] Let the woman learn in silence with all subjection. [12] But I suffer not a woman to teach, nor to usurp authority over the man, but to be in silence.
See All...). To stand up in front of a group and teach is to be in authority in that situation. A book can easily be picked up or laid aside. It is not controlling a service or the reader in any authoritative way.

I believe the scriptural injunction is against ladies taking (usurping) authority over men in a church meeting. Teaching is included because it was one of the ways they can do that. However, I do not believe that women are restricted from studying, learning, and presenting that learning in other situations. The Bible teaches us that Aquila and Priscilla took Apollos aside and "expounded unto him the way of God more perfectly" (Acts 18:26And he began to speak boldly in the synagogue: whom when Aquila and Priscilla had heard, they took him unto them, and expounded unto him the way of God more perfectly.
See All...). This husband and wife team worked together to teach Apollos correct doctrine. It was allowed because a woman was not taking control of a church service.

I find that many ladies are astute students of the Bible. Difference in church position does not mean difference in ability. I believe we should encourage Christian ladies to study God's word with all their hearts. Then, we should find scriptural means for them to help others with that which God has given them. I believe that one of those ways is writing.