Revelation 22.18; does God mean what He says?

I recently had occasion to read Dr. Norman Spurgeon MacPherson's book "Tell It Like It Will Be". In this concise and well written work, the author critically examines the pre-tribulation rapture theory against what is written in God's word.

On page 29 MacPherson writes;

 "The pre-tribulationist believes in three resurrections: the "first" resurrection of Rev. 20.5, the second resurrection that follows the millennium, and a "first" some seven years prior to the "first" mentioned in Rev. 20. This takes place before the great tribulation at the coming of Christ to take away the Church. Although in no place in the New Testament does it state there will be a coming and resurrection prior to the tribulation, their belief that the Church will not be in the tribulation necessitates this assumption. They cannot think of the "first resurrection" of Rev. 20.5 being actually the first because there it states that martyrs under the Antichrist, who is the chief figure in the tribulation, share in the "first resurrection" which would make it necessary for them to believe in the Church passing through the tribulation. My personal conviction is that to assume a first resurrection takes place before the "first resurrection" explicitly referred to in Scripture is a case of adding to Scripture which, according to Rev. 22.18, carries with it a very severe penalty, if deliberate.

Dr MacPherson adds the caveat "if deliberate", and I can well understand this, but when I read God's written word, the admonishment is "Let NO man deceive you" Eph. 5.6, 2 Thess. 2.3, 1 Cor. 3.18, and UMPTEEN other verses beside! Whether willingly, or blindly deceived, is not the final result the same- do not the deceiver and deceived "both fall into the ditch" Matt. 15.14, Luke 6.39?
However, God's word informs us that there awaits a greater condemnation (heavier condemnation (RV)) for those who would be teachers (James 3.1).

Now, I find it impossible that those who teach from the Bible would knowingly deceive themselves, for why would a 'believer' do such? It was said of the princes of this world that had they known it, they would not have crucified the Lord of glory. 1 Cor. 2.8. Admittedly, that was the ultimate crime! however, the psalmist says For thou hast magnified thy word above all thy name, Psalm 138.2, so, is it a light thing to add to what is written? The thought of doing so should make us tremble! but, I fear that as peddling His word has become so commercialised today, many evangelicals would seem to be devoid of godly fear, making merchandise of God's word (John 2.16, 2 Pet. 2.2-3 etc). The pre-trib bandwagon is big business for many; it is not just books but films as well, most notably the 'Left Behind' series. Deception is a peculiar thing when we think about it, from where I am sitting, I can only believe that it is fame and the financial 'reward' that comes with it to be the (only? primary?) motivating factor to deceive. The Bible teaches us that it was covetousness that ensnared Balaam: 2 Pet. 2. 14-16, Jude 11. It was reward that was the error of Balaam, and Jude says he ran greedily after it. Balaam's 'reward' was the wages of unrighteousness (2.Pet. 2.15). When we do anything contrary to what God would have us do, are we not walking toward danger? On this theme, 1 Tim. 6.10 says the love of money is the root of all evil, mark that the apostle said all evil! (my emphasis). The RV says a root, as opposed to the root, nevertheless, he goes on to say, which while some coveted after, they have erred from the faith, and pierced themselves through with many sorrows. (my emphasis). It is clear to me, at any rate, that when those who teach from God's Book know that what they are teaching is error, and continue to receive an income from it, surely they are speaking lies in hypocrisy; having their conscience seared ?(1 Tim. 4.2). The greater the reward these evangelical peddlers receive, the more danger they are in. Those who receive little, or nothing, are more likely to recant should they be convicted of their error, for they have less motivation to go on deceiving.

Is teaching a first resurrection before the first resurrection, (for that is what the pre-tribulation rapture theory amounts to!) adding to God's word? This is a fearful thing to consider in light of the Lord's words in Rev. 22.18, but will an honest mind say otherwise?