The Seventh-Day Adventist Church has been the subject of some very strange, bizarre and also remarkably prejudiced research projects, public statements, and literary works. This state of affairs is aided and abetted by the fact that a large proportion of those who claim to be SDA church members do not really know the doctrines of the church, or the Bible in general!
However, it is an orthodox Christian church, and it seems to be a surprise to many that Adventists can honestly agree with the Apostle's Creed (with that all-important caveat of that small 'c' in 'catholic'). It is unquestionably a denomination that traces its heritage back through the Reformation. However, this denomination does not accept the keeping of the first day of the week, as it finds absolutely no Scriptural basis for the keeping of Sunday (the first day of the week) as Sabbath instead of Saturday (the seventh-day of the week) as stipulated by the fourth commandment. In this regard it finds itself to be a Protestant denomination that in fact respectfully protests against the Protestants, including with regard to the suggestion that the New Testament sanctions any change to the fourth commandment, or the substitution of the so-called 'Lord's Day' for the fourth-commandment Sabbath. Seventh-Day Adventism recognises the literal sanctity of all ten commandments, and finds no Scriptural justification for subjection of the fourth commandment to interpretation and change.
Indeed, as a believing Adventist Christian, I fully contend that if an explicitly-worded commandment can be over-ruled by theological artifices constructed after the fact, quite why the same hermeneutical approach should not apply to the other nine (i.e. that they can also be over-ruled, and that God should find that acceptable) is a question that in my experience has never once been answered satisfactorily by any confessional Christian who does actually believe in the other nine commandments!
The Seventh-Day Adventist Church certainly acknowledges that true Christian belief and piety can - and does - exist outside the SDA church, This would, arguably constitute an acknowledgement of the genuine catholicity of the Christian Church (we would also acknowledge the fact that many who claim to be Adventists do so in name only). However, full and unstinting participation in the ecumenical movement is extremely difficult for serious and confessional Adventists, given the radical differences in theological outlook that separate them from other Christian denominations. However, Adventism operates differently in different parts of the world. Some SDA church members are very keen to be seen as just another part of the Christian family, and are uncomfortable with certain Adventist doctrines that differ from the 'mainstream.' Such church members actively pursue ecumenical participation. Others are actively and vociferously anti-everything that is non-Adventist - and proud of it. However, this link provides some clear and accurate information regarding the SDA response to the ecumenical movement.
Despite some ludicrous and ill-founded assumptions to this effect, the Seventh-Day Adventist Church in the UK is unquestionably NOT a part of the 'Black Majority Church' movement. That said, quietly as some want it to be kept, this church definitely suffers from serious problems in the area of race relations on all sides of various cultural divides - just like many other denominations on the planet. However, all true Christian believers would agree that the Gospel does not recognise the superiority or inferiority of any given race or culture.
The overall theological position of the Adventist church is at the 'conservative' end of the spectrum, and its doctrinal positions are serious and unambiguous. Nevertheless, a good proportion of Adventists are very keen to share the essentials of Christian faith alongside other Christian believers. Intriguingly, a health message and temperance pledge are a major part of Seventh-Day Adventism, and it is understood that physical health is a crucial part of spiritual life, given that the body 'is a temple.'
The Seventh-Day Adventist church is absolutely committed to the Reformation principle of sola scriptura. This link to the official world church website provides a more specific theological insight into the specific doctrines and beliefs of the Seventh-Day Adventist Church:
http://www.adventist.org/beliefs/fundamental/