No it's not.
An appeal to authority would be if I said that because they said it, it must be true. An extreme appeal to authority is the appeal to experts, name-dropping theologians like Paul Tillich.
An idea you happen to agree with already that you then find in a book used by your church just reinforces the notion that your beliefs are orthodox. But if you came to that conclusion yourself, you're not using their authority, you're just agreeing with their opinion here.
My actual beliefs concerning this came from doing therapy, and reading two books in particular. The Gifts of Imperfection (Brene Brown) and When Panic Attacks (David Burns), I had found under different circumstances. The second was part of the therapy book that I was asked to read (I didn't until later), and the first something I found at Amazon. Both of these were about letting go of the perfect and being your best self, not the best. But more importantly, I was learning this firsthand working for Amazon.