A Scientology book titled "Theology & Practice of a Contemporary Religion Scientology", (Bridge Publications, 1998. ISBN 1-57318-145-5) includes Bryan R. Wilson's essay "Scientology - An Analysis and Comparison of its Religion Systems and Doctrines". In this he says "Scientology differs radically from traditional Christian churches [ ... ] in matters of ideology, practice and organisation."
On the subject of dual membership with Scientology and other faiths, Dr Wilson says
"I have spoken with senior Church officials as well as individual Scientologists on the this aspect of Scientology and their response was that while exclusivity is not required, it comes about as a matter of practice. According to them, as one becomes more involved with Scientology, one inevitably discards one's prior faith. For example, my experience is that a Jew who becomes a Scientologist might remain affiliated with Judaism for cultural reasons and might celebrate Jewish holidays with family and friends, but he or she would not practise and would not believe in Jewish theology. From my view as a scholar this explanation seems correct. Scientologists regard their faith as a complete religion demanding dedication of its members."
As a Christian, you look to the bible for the word of God. It's in there you find God's revelation to mankind. You don't look else where for it.
New recruits to the Church of Scientology are told that they can practice their religion of choice and Scientology at the same time. The official introductory handbook "What is Scientology?" (1992) states (p 544):
"In Scientology there is no attempt to change a person's beliefs or to persuade him away from any religion to which he already belongs."
"Scientology is all-denominational in that it opens its membership to people of all faiths."
"Membership in Scientology does not mean that there is any necessity to leave your current church, synagogue, temple or mosque."
"Scientology respects all religions. Scientology does not conflict with other religions or other religious practices"