I have been to sermons quite a few times at the SDA. I'm not that knowlegable of their theology, but overall I enjoyed being there. One of the founders of the SDA was Ellen G. White, who was some kind of prophetess. I don't know what part her visions and teachings have in the church, maybe someome else could share more about this?
What Ellen White's work consists of.
[Ellen G. White] wrote more than 5,000 periodical articles and 40 books; but today, including compilations from her 50,000 pages of manuscript, more than 100 titles are available in English. She is the most translated woman writer in the entire history of literature, and the most translated American author of either gender. Her writings cover a broad range of subjects, including religion, education, social relationships, evangelism, prophecy, publishing, nutrition, and management.
What the SDA church says about Ellen White.
The SDA Fundamentals - Article 18
18. The Gift of Prophecy
The Scriptures testify that one of the gifts of the Holy Spirit is prophecy.
This gift is an identifying mark of the remnant church and we believe it was manifested in the ministry of Ellen G. White. Her writings speak with prophetic authority and provide comfort, guidance, instruction, and correction to the church.
They also make clear that the Bible is the standard by which all teaching and experience must be tested.
(Supporting scripture for what a prophet is: Numbers 12:6; 2 Chronicles 20:20; Amos 3:7; Joel 2:28-29; Acts of the Apostles 2:14-21; 2 Timothy 3:16-17; Hebrews 1:1-3; Revelation 12:17; Revelation 19:10, Revelation 22:8-9)
Ellen's own words concerning her writings.
NOTE: There are more resources on this subject from the church stance, but I thought her own words would be the best to present here. The Spirit of Prophecy (a prophet) must be in line with scripture. "To the law and to the testimony: if they speak not according to this word, it is because there is no light in them." —Isaiah 8:20
Her words:
My opinion as a long-time SDA member.
Her writings are incredible. The number of subjects she wrote about, authoritatively and knowledgeably, is mind-boggling. Her writings on scripture and prophecy are extensive.
But what about the woman? When you start reading her work and you get a feel for her character, you can tell she was a righteous, Godly woman. What isn't apparent in her formal writings is that she went through great hardship and struggle in life. I recommend reading her biography to understand the woman behind the writings. Where she came from and what her life was like.
I do believe she was a prophet, based on what I've read from her writings and how they align with scripture.
What I think is just my opinion. It's up to the reader to decide what they think about Ellen. A person should read what she has to say and come away with their own conclusion.
All of her writings are available free online from her estate
here (newer) and
here (older, more straight-forward). Also via smart device app called EGW Writings 2 for both iPhone and Android. There's even an older
research edition for the PC from 2007 ($15 donation), which I use regularly.